From c25544735bf3a06a0090365aa89f43debad7b7dd Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 6 Apr 2022 19:36:51 -0500 Subject: [PATCH] treewide: uapi: Replace zero-length arrays with flexible-array members MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. This code was transformed with the help of Coccinelle: (linux-5.19-rc2$ spatch --jobs $(getconf _NPROCESSORS_ONLN) --sp-file script.cocci --include-headers --dir . > output.patch) @@ identifier S, member, array; type T1, T2; @@ struct S { ... T1 member; T2 array[ - 0 ]; }; -fstrict-flex-arrays=3 is coming and we need to land these changes to prevent issues like these in the short future: ../fs/minix/dir.c:337:3: warning: 'strcpy' will always overflow; destination buffer has size 0, but the source string has length 2 (including NUL byte) [-Wfortify-source] strcpy(de3->name, "."); ^ Since these are all [0] to [] changes, the risk to UAPI is nearly zero. If this breaks anything, we can use a union with a new member name. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays Link: https://github.com/KSPP/linux/issues/78 Build-tested-by: kernel test robot Link: https://lore.kernel.org/lkml/62b675ec.wKX6AOZ6cbE71vtF%25lkp@intel.com/ Acked-by: Dan Williams # For ndctl.h Signed-off-by: Gustavo A. R. Silva --- include/uapi/linux/perf_event.h | 2 +- include/uapi/linux/pkt_cls.h | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 0474ee3..03b3700 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -494,7 +494,7 @@ struct perf_event_query_bpf { /* * User provided buffer to store program ids */ - __u32 ids[0]; + __u32 ids[]; }; /* diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h index 1215377..3faee01 100644 --- a/include/uapi/linux/pkt_cls.h +++ b/include/uapi/linux/pkt_cls.h @@ -180,7 +180,7 @@ struct tc_u32_sel { short hoff; __be32 hmask; - struct tc_u32_key keys[0]; + struct tc_u32_key keys[]; }; struct tc_u32_mark { @@ -192,7 +192,7 @@ struct tc_u32_mark { struct tc_u32_pcnt { __u64 rcnt; __u64 rhit; - __u64 kcnts[0]; + __u64 kcnts[]; }; /* Flags */