Extend libbpf attach opts and add a new detach opts API so this can be used
to add/remove fd-based tcx BPF programs. The old-style bpf_prog_detach() and
bpf_prog_detach2() APIs are refactored to reuse the new bpf_prog_detach_opts()
internally.
The bpf_prog_query_opts() API got extended to be able to handle the new
link_ids, link_attach_flags and revision fields.
For concrete usage examples, see the extensive selftests that have been
developed as part of this series.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230719140858.13224-4-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
realloc() and reallocarray() can either return NULL or a special
non-NULL pointer, if their size argument is zero. This requires a bit
more care to handle NULL-as-valid-result situation differently from
NULL-as-error case. This has caused real issues before ([0]), and just
recently bit again in production when performing bpf_program__attach_usdt().
This patch fixes 4 places that do or potentially could suffer from this
mishandling of NULL, including the reported USDT-related one.
There are many other places where realloc()/reallocarray() is used and
NULL is always treated as an error value, but all those have guarantees
that their size is always non-zero, so those spot don't need any extra
handling.
[0] d08ab82f59d5 ("libbpf: Fix double-free when linker processes empty sections")
Fixes: 999783c8bbda ("libbpf: Wire up spec management and other arch-independent USDT logic")
Fixes: b63b3c490eee ("libbpf: Add bpf_program__set_insns function")
Fixes: 697f104db8a6 ("libbpf: Support custom SEC() handlers")
Fixes: b12688267280 ("libbpf: Change the order of data and text relocations.")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230711024150.1566433-1-andrii@kernel.org
Don't reset recorded sec_def handler unconditionally on
bpf_program__set_type(). There are two situations where this is wrong.
First, if the program type didn't actually change. In that case original
SEC handler should work just fine.
Second, catch-all custom SEC handler is supposed to work with any BPF
program type and SEC() annotation, so it also doesn't make sense to
reset that.
This patch fixes both issues. This was reported recently in the context
of breaking perf tool, which uses custom catch-all handler for fancy BPF
prologue generation logic. This patch should fix the issue.
[0] https://lore.kernel.org/linux-perf-users/ab865e6d-06c5-078e-e404-7f90686db50d@amd.com/
Fixes: d6e6286a12e7 ("libbpf: disassociate section handler on explicit bpf_program__set_type() call")
Reported-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230707231156.1711948-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Andrii Nakryiko writes:
And we currently don't have an attach type for NETLINK BPF link.
Thankfully it's not too late to add it. I see that link_create() in
kernel/bpf/syscall.c just bypasses attach_type check. We shouldn't
have done that. Instead we need to add BPF_NETLINK attach type to enum
bpf_attach_type. And wire all that properly throughout the kernel and
libbpf itself.
This adds BPF_NETFILTER and uses it. This breaks uabi but this
wasn't in any non-rc release yet, so it should be fine.
v2: check link_attack prog type in link_create too
Fixes: 84601d6ee68a ("bpf: add bpf_link support for BPF_NETFILTER programs")
Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/CAEf4BzZ69YgrQW7DHCJUT_X+GqMq_ZQQPBwopaJJVGFD5=d5Vg@mail.gmail.com/
Link: https://lore.kernel.org/bpf/20230605131445.32016-1-fw@strlen.de
Make sure that libbpf code always gets FD with O_CLOEXEC flag set,
regardless if file is open through open() or fopen(). For the latter
this means to add "e" to mode string, which is supported since pretty
ancient glibc v2.7.
Also drop the outdated TODO comment in usdt.c, which was already completed.
Suggested-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230525221311.2136408-1-andrii@kernel.org
This patch updates bpf_map__set_value_size() so that if the given map is
memory mapped, it will attempt to resize the mapped region. Initial
contents of the mapped region are preserved. BTF is not required, but
after the mapping is resized an attempt is made to adjust the associated
BTF information if the following criteria is met:
- BTF info is present
- the map is a datasec
- the final variable in the datasec is an array
... the resulting BTF info will be updated so that the final array
variable is associated with a new BTF array type sized to cover the
requested size.
Note that the initial resizing of the memory mapped region can succeed
while the subsequent BTF adjustment can fail. In this case, BTF info is
dropped from the map by clearing the key and value type.
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20230524004537.18614-2-inwardvessel@gmail.com
Signed-off-by: Daniel Müller <deso@posteo.net>
Currently, libbpf leaves `call #0` instruction for __weak unresolved
kfuncs, which might lead to a confusing verifier log situations, where
invalid `call #0` will be treated as successfully validated.
We can do better. Libbpf already has an established mechanism of
poisoning instructions that failed some form of resolution (e.g., CO-RE
relocation and BPF map set to not be auto-created). Libbpf doesn't fail
them outright to allow users to guard them through other means, and as
long as BPF verifier can prove that such poisoned instructions cannot be
ever reached, this doesn't consistute an invalid BPF program. If user
didn't guard such code, libbpf will extract few pieces of information to
tie such poisoned instructions back to additional information about what
entitity wasn't resolved (e.g., BPF map name, or CO-RE relocation
information).
__weak unresolved kfuncs fit this model well, so this patch extends
libbpf with poisioning and log fixup logic for kfunc calls.
Note, this poisoning is done only for kfunc *calls*, not kfunc address
resolution (ldimm64 instructions). The former cannot be ever valid, if
reached, so it's safe to poison them. The latter is a valid mechanism to
check if __weak kfunc ksym was resolved, and do necessary guarding and
work arounds based on this result, supported in most recent kernels. As
such, libbpf keeps such ldimm64 instructions as loading zero, never
poisoning them.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230418002148.3255690-4-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Currently libbpf always reports "kernel" as a source of ksym BTF type,
which is ambiguous given ksym's BTF can come from either vmlinux or
kernel module BTFs. Make this explicit and log module name, if used BTF
is from kernel module.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230418002148.3255690-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Normalize internal constants, field names, and comments related to log
fixup. Also add explicit `ext_idx` alias for relocation where relocation
is pointing to extern description for additional information.
No functional changes, just a clean up before subsequent additions.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230418002148.3255690-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
If user explicitly overrides programs's type with
bpf_program__set_type() API call, we need to disassociate whatever
SEC_DEF handler libbpf determined initially based on program's SEC()
definition, as it's not goind to be valid anymore and could lead to
crashes and/or confusing failures.
Also, fix up bpf_prog_test_load() helper in selftests/bpf, which is
force-setting program type (even if that's completely unnecessary; this
is quite a legacy piece of code), and thus should expect auto-attach to
not work, yet one of the tests explicitly relies on auto-attach for
testing.
Instead, force-set program type only if it differs from the desired one.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230327185202.1929145-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Müller <deso@posteo.net>
bpf_map__attach_struct_ops() was creating a dummy bpf_link as a
placeholder, but now it is constructing an authentic one by calling
bpf_link_create() if the map has the BPF_F_LINK flag.
You can flag a struct_ops map with BPF_F_LINK by calling
bpf_map__set_map_flags().
Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230323032405.3735486-5-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Write data to fd by calling "vdprintf", in most implementations
of the standard library, the data is finally written by the writev syscall.
But "uprobe_events/kprobe_events" does not allow segmented writes,
so switch the "append_to_file" function to explicit write() call.
Signed-off-by: Liu Pan <patteliu@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230320030720.650-1-patteliu@gmail.com
void *p = kfunc; -> generates ld_imm64 insn.
kfunc() -> generates bpf_call insn.
libbpf patches bpf_call insn correctly while only btf_id part of ld_imm64 is
set in the former case. Which means that pointers to kfuncs in modules are not
patched correctly and the verifier rejects load of such programs due to btf_id
being out of range. Fix libbpf to patch ld_imm64 for kfunc.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230317201920.62030-3-alexei.starovoitov@gmail.com
By default, libbpf will attach the kprobe/uprobe BPF program in the
latest mode that supported by kernel. In this patch, we add the support
to let users manually attach kprobe/uprobe in legacy or perf mode.
There are 3 mode that supported by the kernel to attach kprobe/uprobe:
LEGACY: create perf event in legacy way and don't use bpf_link
PERF: create perf event with perf_event_open() and don't use bpf_link
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Link: create perf event with perf_event_open() and use bpf_link
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com
Users now can manually choose the mode with
bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
This change adds support for attaching uprobes to shared objects located
in APKs, which is relevant for Android systems where various libraries
may reside in APKs. To make that happen, we extend the syntax for the
"binary path" argument to attach to with that supported by various
Android tools:
<archive>!/<binary-in-archive>
For example:
/system/app/test-app/test-app.apk!/lib/arm64-v8a/libc++_shared.so
APKs need to be specified via full path, i.e., we do not attempt to
resolve mere file names by searching system directories.
We cannot currently test this functionality end-to-end in an automated
fashion, because it relies on an Android system being present, but there
is no support for that in CI. I have tested the functionality manually,
by creating a libbpf program containing a uretprobe, attaching it to a
function inside a shared object inside an APK, and verifying the sanity
of the returned values.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230301212308.1839139-4-deso@posteo.net
This change splits the elf_find_func_offset() function in two:
elf_find_func_offset(), which now accepts an already opened Elf object
instead of a path to a file that is to be opened, as well as
elf_find_func_offset_from_file(), which opens a binary based on a
path and then invokes elf_find_func_offset() on the Elf object. Having
this split in responsibilities will allow us to call
elf_find_func_offset() from other code paths on Elf objects that did not
necessarily come from a file on disk.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230301212308.1839139-3-deso@posteo.net
Add option to set when the perf buffer should wake up, by default the
perf buffer becomes signaled for every event that is being pushed to it.
In case of a high throughput of events it will be more efficient to wake
up only once you have X events ready to be read.
So your application can wakeup once and drain the entire perf buffer.
Signed-off-by: Jon Doron <jond@wiz.io>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230207081916.3398417-1-arilou@gmail.com
In a previous commit, Ubuntu kernel code version is correctly set
by retrieving the information from /proc/version_signature.
commit<5b3d72987701d51bf31823b39db49d10970f5c2d>
(libbpf: Improve LINUX_VERSION_CODE detection)
The /proc/version_signature file doesn't present in at least the
older versions of Debian distributions (eg, Debian 9, 10). The Debian
kernel has a similar issue where the release information from uname()
syscall doesn't give the kernel code version that matches what the
kernel actually expects. Below is an example content from Debian 10.
release: 4.19.0-23-amd64
version: #1 SMP Debian 4.19.269-1 (2022-12-20) x86_64
Debian reports incorrect kernel version in utsname::release returned
by uname() syscall, which in older kernels (Debian 9, 10) leads to
kprobe BPF programs failing to load due to the version check mismatch.
Fortunately, the correct kernel code version presents in the
utsname::version returned by uname() syscall in Debian kernels. This
change adds another get kernel version function to handle Debian in
addition to the previously added get kernel version function to handle
Ubuntu. Some minor refactoring work is also done to make the code more
readable.
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230203234842.2933903-1-hao.xiang@bytedance.com
In a prior change, the verifier was updated to support sleepable
BPF_PROG_TYPE_STRUCT_OPS programs. A caller could set the program as
sleepable with bpf_program__set_flags(), but it would be more ergonomic
and more in-line with other sleepable program types if we supported
suffixing a struct_ops section name with .s to indicate that it's
sleepable.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230125164735.785732-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
'.' is not allowed in the event name of kprobe. Therefore, we will get a
EINVAL if the kernel function name has a '.' in legacy kprobe attach
case, such as 'icmp_reply.constprop.0'.
In order to adapt this case, we need to replace the '.' with other char
in gen_kprobe_legacy_event_name(). And I use '_' for this propose.
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com
Clang warns on 32-bit ARM on this comparision:
libbpf.c:10497:18: error: result of comparison of constant 4294967296 with expression of type 'size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Typecast ref_ctr_off to __u64 in the check conditional, it is false on
32bit anyways.
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221219191526.296264-1-raj.khem@gmail.com
Currently LLVM fails to recognize .data.* as data section and defaults to .text
section. Later BPF backend tries to emit 4-byte NOP instruction which doesn't
exist in BPF ISA and aborts.
The fix for LLVM is pending:
https://reviews.llvm.org/D138477
While waiting for the fix lets workaround the linked_list test case
by using .bss.* prefix which is properly recognized by LLVM as BSS section.
Fix libbpf to support .bss. prefix and adjust tests.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Fixed following checkpatch issues:
WARNING: Block comments use a trailing */ on a separate line
+ * other BPF program's BTF object */
WARNING: Possible repeated word: 'be'
+ * name. This is important to be be able to find corresponding BTF
ERROR: switch and case should be at the same indent
+ switch (ext->kcfg.sz) {
+ case 1: *(__u8 *)ext_val = value; break;
+ case 2: *(__u16 *)ext_val = value; break;
+ case 4: *(__u32 *)ext_val = value; break;
+ case 8: *(__u64 *)ext_val = value; break;
+ default:
ERROR: trailing statements should be on next line
+ case 1: *(__u8 *)ext_val = value; break;
ERROR: trailing statements should be on next line
+ case 2: *(__u16 *)ext_val = value; break;
ERROR: trailing statements should be on next line
+ case 4: *(__u32 *)ext_val = value; break;
ERROR: trailing statements should be on next line
+ case 8: *(__u64 *)ext_val = value; break;
ERROR: code indent should use tabs where possible
+ }$
WARNING: please, no spaces at the start of a line
+ }$
WARNING: Block comments use a trailing */ on a separate line
+ * for faster search */
ERROR: code indent should use tabs where possible
+^I^I^I^I^I^I &ext->kcfg.is_signed);$
WARNING: braces {} are not necessary for single statement blocks
+ if (err) {
+ return err;
+ }
ERROR: code indent should use tabs where possible
+^I^I^I^I sizeof(*obj->btf_modules), obj->btf_module_cnt + 1);$
Signed-off-by: Kang Minchul <tegongkang@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20221113190648.38556-3-tegongkang@gmail.com
An update for libbpf's hashmap interface from void* -> void* to a
polymorphic one, allowing both long and void* keys and values.
This simplifies many use cases in libbpf as hashmaps there are mostly
integer to integer.
Perf copies hashmap implementation from libbpf and has to be
updated as well.
Changes to libbpf, selftests/bpf and perf are packed as a single
commit to avoid compilation issues with any future bisect.
Polymorphic interface is acheived by hiding hashmap interface
functions behind auxiliary macros that take care of necessary
type casts, for example:
#define hashmap_cast_ptr(p) \
({ \
_Static_assert((p) == NULL || sizeof(*(p)) == sizeof(long),\
#p " pointee should be a long-sized integer or a pointer"); \
(long *)(p); \
})
bool hashmap_find(const struct hashmap *map, long key, long *value);
#define hashmap__find(map, key, value) \
hashmap_find((map), (long)(key), hashmap_cast_ptr(value))
- hashmap__find macro casts key and value parameters to long
and long* respectively
- hashmap_cast_ptr ensures that value pointer points to a memory
of appropriate size.
This hack was suggested by Andrii Nakryiko in [1].
This is a follow up for [2].
[1] https://lore.kernel.org/bpf/CAEf4BzZ8KFneEJxFAaNCCFPGqp20hSpS2aCj76uRk3-qZUH5xg@mail.gmail.com/
[2] https://lore.kernel.org/bpf/af1facf9-7bc8-8a3d-0db4-7b3f333589a2@meta.com/T/#m65b28f1d6d969fcd318b556db6a3ad499a42607d
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221109142611.879983-2-eddyz87@gmail.com
Teach libbpf to not add BPF_F_MMAPABLE flag unnecessarily for ARRAY maps
that are backing data sections, if such data sections don't expose any
variables to user-space. Exposed variables are those that have
STB_GLOBAL or STB_WEAK ELF binding and correspond to BTF VAR's
BTF_VAR_GLOBAL_ALLOCATED linkage.
The overall idea is that if some data section doesn't have any variable that
is exposed through BPF skeleton, then there is no reason to make such
BPF array mmapable. Making BPF array mmapable is not a free no-op
action, because BPF verifier doesn't allow users to put special objects
(such as BPF spin locks, RB tree nodes, linked list nodes, kptrs, etc;
anything that has a sensitive internal state that should not be modified
arbitrarily from user space) into mmapable arrays, as there is no way to
prevent user space from corrupting such sensitive state through direct
memory access through memory-mapped region.
By making sure that libbpf doesn't add BPF_F_MMAPABLE flag to BPF array
maps corresponding to data sections that only have static variables
(which are not supposed to be visible to user space according to libbpf
and BPF skeleton rules), users now can have spinlocks, kptrs, etc in
either default .bss/.data sections or custom .data.* sections (assuming
there are no global variables in such sections).
The only possible hiccup with this approach is the need to use global
variables during BPF static linking, even if it's not intended to be
shared with user space through BPF skeleton. To allow such scenarios,
extend libbpf's STV_HIDDEN ELF visibility attribute handling to
variables. Libbpf is already treating global hidden BPF subprograms as
static subprograms and adjusts BTF accordingly to make BPF verifier
verify such subprograms as static subprograms with preserving entire BPF
verifier state between subprog calls. This patch teaches libbpf to treat
global hidden variables as static ones and adjust BTF information
accordingly as well. This allows to share variables between multiple
object files during static linking, but still keep them internal to BPF
program and not get them exposed through BPF skeleton.
Note, that if the user has some advanced scenario where they absolutely
need BPF_F_MMAPABLE flag on .data/.bss/.rodata BPF array map despite
only having static variables, they still can achieve this by forcing it
through explicit bpf_map__set_map_flags() API.
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20221019002816.359650-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Refactor libbpf's BTF fixup step during BPF object open phase. The only
functional change is that we now ignore BTF_VAR_GLOBAL_EXTERN variables
during fix up, not just BTF_VAR_STATIC ones, which shouldn't cause any
change in behavior as there shouldn't be any extern variable in data
sections for valid BPF object anyways.
Otherwise it's just collapsing two functions that have no reason to be
separate, and switching find_elf_var_offset() helper to return entire
symbol pointer, not just its offset. This will be used by next patch to
get ELF symbol visibility.
While refactoring, also "normalize" debug messages inside
btf_fixup_datasec() to follow general libbpf style and print out data
section name consistently, where it's available.
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20221019002816.359650-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When there are no program sections, obj->programs is left unallocated,
and find_prog_by_sec_insn()'s search lands on &obj->programs[0] == NULL,
and will cause null-pointer dereference in the following access to
prog->sec_idx.
Guard the search with obj->nr_programs similar to what's being done in
__bpf_program__iter() to prevent null-pointer access from happening.
Fixes: db2b8b06423c ("libbpf: Support CO-RE relocations for multi-prog sections")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221012022353.7350-4-shung-hsi.yu@suse.com
ELF section data pointer returned by libelf may be NULL (if section has
SHT_NOBITS), so null check section data pointer before attempting to
copy license and kversion section.
Fixes: cb1e5e961991 ("bpf tools: Collect version and license from ELF sections")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221012022353.7350-3-shung-hsi.yu@suse.com
This commit replace e_shnum with the elf_getshdrnum() helper to fix two
oss-fuzz-reported heap-buffer overflow in __bpf_object__open. Both
reports are incorrectly marked as fixed and while still being
reproducible in the latest libbpf.
# clusterfuzz-testcase-minimized-bpf-object-fuzzer-5747922482888704
libbpf: loading object 'fuzz-object' from buffer
libbpf: sec_cnt is 0
libbpf: elf: section(1) .data, size 0, link 538976288, flags 2020202020202020, type=2
libbpf: elf: section(2) .data, size 32, link 538976288, flags 202020202020ff20, type=1
=================================================================
==13==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6020000000c0 at pc 0x0000005a7b46 bp 0x7ffd12214af0 sp 0x7ffd12214ae8
WRITE of size 4 at 0x6020000000c0 thread T0
SCARINESS: 46 (4-byte-write-heap-buffer-overflow-far-from-bounds)
#0 0x5a7b45 in bpf_object__elf_collect /src/libbpf/src/libbpf.c:3414:24
#1 0x5733c0 in bpf_object_open /src/libbpf/src/libbpf.c:7223:16
#2 0x5739fd in bpf_object__open_mem /src/libbpf/src/libbpf.c:7263:20
...
The issue lie in libbpf's direct use of e_shnum field in ELF header as
the section header count. Where as libelf implemented an extra logic
that, when e_shnum == 0 && e_shoff != 0, will use sh_size member of the
initial section header as the real section header count (part of ELF
spec to accommodate situation where section header counter is larger
than SHN_LORESERVE).
The above inconsistency lead to libbpf writing into a zero-entry calloc
area. So intead of using e_shnum directly, use the elf_getshdrnum()
helper provided by libelf to retrieve the section header counter into
sec_cnt.
Fixes: 0d6988e16a12 ("libbpf: Fix section counting logic")
Fixes: 25bbbd7a444b ("libbpf: Remove assumptions about uniqueness of .rodata/.data/.bss maps")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=40868
Link: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=40957
Link: https://lore.kernel.org/bpf/20221012022353.7350-2-shung-hsi.yu@suse.com
When running rootless with special capabilities like:
FOWNER / DAC_OVERRIDE / DAC_READ_SEARCH
The "access" API will not make the proper check if there is really
access to a file or not.
>From the access man page:
"
The check is done using the calling process's real UID and GID, rather
than the effective IDs as is done when actually attempting an operation
(e.g., open(2)) on the file. Similarly, for the root user, the check
uses the set of permitted capabilities rather than the set of effective
capabilities; ***and for non-root users, the check uses an empty set of
capabilities.***
"
What that means is that for non-root user the access API will not do the
proper validation if the process really has permission to a file or not.
To resolve this this patch replaces all the access API calls with
faccessat with AT_EACCESS flag.
Signed-off-by: Jon Doron <jond@wiz.io>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220925070431.1313680-1-arilou@gmail.com
