From 7a7d4237e338061616ad6cdb3a3f08ad391ca904 Mon Sep 17 00:00:00 2001 From: Anton Protopopov Date: Wed, 3 Apr 2024 14:33:03 +0200 Subject: [PATCH] bpf: Pack struct bpf_fib_lookup [ 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+R1VtFiLrw@mail.gmail.com/#t Reported-by: Naresh Kamboju Fixes: e1850ea9bd9e ("bpf: bpf_fib_lookup return MTU value as output when looked up") Signed-off-by: Anton Protopopov Signed-off-by: Andrii Nakryiko Reviewed-by: Alexander Lobakin Acked-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20240403123303.1452184-1-aspsk@isovalent.com Signed-off-by: Sasha Levin --- 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 366df8a1a5fc..fb09fd1767f2 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -6994,7 +6994,7 @@ 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 366df8a1a5fc..fb09fd1767f2 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -6994,7 +6994,7 @@ 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 */