6.1-stable review patch. If anyone has any objections, please let me know.
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From: Anton Protopopov aspsk@isovalent.com
[ Upstream commit f91717007217d975aa975ddabd91ae1a107b9bff ]
The struct bpf_fib_lookup is supposed to be of size 64. A recent commit 59b418c7063d ("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+R1VtFi...
Reported-by: Naresh Kamboju naresh.kamboju@linaro.org Fixes: e1850ea9bd9e ("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 --- include/uapi/linux/bpf.h | 2 +- tools/include/uapi/linux/bpf.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index d5d2183730b9f..a17688011440e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -6730,7 +6730,7 @@ struct bpf_fib_lookup {
/* output: MTU value */ __u16 mtu_result; - }; + } __attribute__((packed, aligned(2))); /* input: L3 device index for lookup * output: device index from FIB lookup */ diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index d5d2183730b9f..a17688011440e 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -6730,7 +6730,7 @@ struct bpf_fib_lookup {
/* output: MTU value */ __u16 mtu_result; - }; + } __attribute__((packed, aligned(2))); /* input: L3 device index for lookup * output: device index from FIB lookup */