This is a note to let you know that I've just added the patch titled
bpf: Pack struct bpf_fib_lookup
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-pack-struct-bpf_fib_lookup.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 494586d006e4bcefa1935504ee6f3ecdec570c2b
Author: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
Date: Wed Apr 3 14:33:03 2024 +0200
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@xxxxxxxxxxxxxx/#t
Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
Fixes: e1850ea9bd9e ("bpf: bpf_fib_lookup return MTU value as output when looked up")
Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20240403123303.1452184-1-aspsk@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 754e68ca8744c..83f31916e2635 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7040,7 +7040,7 @@ 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 7f24d898efbb4..a12f597a1c47f 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -7039,7 +7039,7 @@ 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
*/
