]> git.baikalelectronics.ru Git - kernel.git/commit
bpf: Avoid gcc-10 stringop-overflow warning in struct bpf_prog
authorArnd Bergmann <arnd@arndb.de>
Thu, 30 Apr 2020 21:30:47 +0000 (23:30 +0200)
committerDaniel Borkmann <daniel@iogearbox.net>
Mon, 4 May 2020 20:54:42 +0000 (22:54 +0200)
commit6805fc79f8dc39bfc90aaa4cd5b9c2cc470320a6
tree31d9b92c73807fe11c553dbbf5b78770f8fa15d7
parent01acbf9bb35cb35bbc2ad05150e731c9e28c7179
bpf: Avoid gcc-10 stringop-overflow warning in struct bpf_prog

gcc-10 warns about accesses to zero-length arrays:

kernel/bpf/core.c: In function 'bpf_patch_insn_single':
cc1: warning: writing 8 bytes into a region of size 0 [-Wstringop-overflow=]
In file included from kernel/bpf/core.c:21:
include/linux/filter.h:550:20: note: at offset 0 to object 'insnsi' with size 0 declared here
  550 |   struct bpf_insn  insnsi[0];
      |                    ^~~~~~

In this case, we really want to have two flexible-array members,
but that is not possible. Removing the union to make insnsi a
flexible-array member while leaving insns as a zero-length array
fixes the warning, as nothing writes to the other one in that way.

This trick only works on linux-3.18 or higher, as older versions
had additional members in the union.

Fixes: 073a09ee970b ("net: bpf: make eBPF interpreter images read-only")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200430213101.135134-6-arnd@arndb.de
include/linux/filter.h