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6eaa8ee3e2
sysfs__read_build_id() reads ELF note headers from sysfs files. The
note's namesz and descsz fields are used to compute the skip size:
int n = namesz + descsz;
if (n > (int)sizeof(bf))
Both namesz and descsz are size_t from NOTE_ALIGN() of 32-bit note
header fields. Their sum can exceed INT_MAX, overflowing the signed
int n to a negative value. The check n > sizeof(bf) then evaluates
false (negative < positive in signed comparison), and read(fd, bf, n)
reinterprets the negative n as a huge size_t count — the kernel writes
up to MAX_RW_COUNT bytes into the 8192-byte stack buffer.
In practice the overflow is bounded by the sysfs file's actual size,
so a real sysfs notes file won't trigger it organically. But crafted
input (e.g. via a mounted debugfs/sysfs image) could.
Fix by validating namesz and descsz individually against the buffer
size before summing, and change n to size_t to avoid the signed
overflow entirely.
Fixes: f1617b4059 ("perf symbols: Record the build_ids of kernel modules too")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>