This is a note to let you know that I've just added the patch titled
bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD
to the 5.15-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-avoid-uninitialized-value-in-bpf_core_read_bitfi.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fd890a29bdf28db6c8e96d8c814e73a24bd69fb3
Author: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx>
Date: Wed May 8 12:13:13 2024 +0200
bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD
[ Upstream commit 009367099eb61a4fc2af44d4eb06b6b4de7de6db ]
[Changes from V1:
- Use a default branch in the switch statement to initialize `val'.]
GCC warns that `val' may be used uninitialized in the
BPF_CRE_READ_BITFIELD macro, defined in bpf_core_read.h as:
[...]
unsigned long long val; \
[...] \
switch (__CORE_RELO(s, field, BYTE_SIZE)) { \
case 1: val = *(const unsigned char *)p; break; \
case 2: val = *(const unsigned short *)p; break; \
case 4: val = *(const unsigned int *)p; break; \
case 8: val = *(const unsigned long long *)p; break; \
} \
[...]
val; \
} \
This patch adds a default entry in the switch statement that sets
`val' to zero in order to avoid the warning, and random values to be
used in case __builtin_preserve_field_info returns unexpected values
for BPF_FIELD_BYTE_SIZE.
Tested in bpf-next master.
No regressions.
Signed-off-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20240508101313.16662-1-jose.marchesi@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h
index e4aa9996a5501..b8e68a17f3f1b 100644
--- a/tools/lib/bpf/bpf_core_read.h
+++ b/tools/lib/bpf/bpf_core_read.h
@@ -101,6 +101,7 @@ enum bpf_enum_value_kind {
case 2: val = *(const unsigned short *)p; break; \
case 4: val = *(const unsigned int *)p; break; \
case 8: val = *(const unsigned long long *)p; break; \
+ default: val = 0; break; \
} \
val <<= __CORE_RELO(s, field, LSHIFT_U64); \
if (__CORE_RELO(s, field, SIGNED)) \
