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Anton Protopopov f654b258e9 bpf: Pack struct bpf_fib_lookup 
[ Upstream commit f917170072 ]

The struct bpf_fib_lookup is supposed to be of size 64. A recent commit
59b418c706 ("bpf: Add a check for struct bpf_fib_lookup size") added
a static assertion to check this property so that future changes to the
structure will not accidentally break this assumption.

As it immediately turned out, on some 32-bit arm systems, when AEABI=n,
the total size of the structure was equal to 68, see [1]. This happened
because the bpf_fib_lookup structure contains a union of two 16-bit
fields:

    union {
            __u16 tot_len;
            __u16 mtu_result;
    };

which was supposed to compile to a 16-bit-aligned 16-bit field. On the
aforementioned setups it was instead both aligned and padded to 32-bits.

Declare this inner union as __attribute__((packed, aligned(2))) such
that it always is of size 2 and is aligned to 16 bits.

  [1] https://lore.kernel.org/all/CA+G9fYtsoP51f-oP_Sp5MOq-Ffv8La2RztNpwvE6+R1VtFiLrw@mail.gmail.com/#t

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Fixes: e1850ea9bd ("bpf: bpf_fib_lookup return MTU value as output when looked up")
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240403123303.1452184-1-aspsk@isovalent.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-06-16 13:39:18 +02:00
..
asm tools arch: Update arch/x86/lib/mem{cpy,set}_64.S copies used in 'perf bench mem memcpy' 2021-05-10 09:01:00 -03:00
asm-generic x86/insn: Use get_unaligned() instead of memcpy() 2021-11-18 19:16:30 +01:00
linux bpf: Fix BTF_ID symbol generation collision in tools/ 2023-10-06 13:18:23 +02:00
nolibc tools/nolibc: fix the O_* fcntl/open macro definitions for riscv 2023-01-18 11:48:56 +01:00
tools tools include: add dis-asm-compat.h to handle version differences 2023-03-17 08:49:04 +01:00
trace/events tools/lib/lockdep: Remove private kernel headers 2017-06-05 09:28:14 +02:00
uapi bpf: Pack struct bpf_fib_lookup 2024-06-16 13:39:18 +02:00
vdso tools headers: Synchronize linux/bits.h with the kernel sources 2020-04-14 11:40:05 -03:00