6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexandre Courbot [ Upstream commit d7231d8cb262b1e350c00271bf53d54414b4f3b1 ] buf_printf() uses a fixed-size stack buffer. vsnprintf() returns the number of bytes that *would* have been written to that buffer, which can be larger than the size of said buffer if the formatted string is too long. The problem is that whenever this happens buf_printf() currently passes this length, unchecked, to buf_write(), which silently reads past the stack buffer and copies invalid data into the output buffer. Fix this by detecting vsnprintf() failures and truncations before appending to the output buffer, and report a fatal error instead of producing corrupt symbol names. Signed-off-by: Alexandre Courbot Link: https://patch.msgid.link/20260527-nova-exports-v2-1-06de4c556d55@nvidia.com Signed-off-by: Nathan Chancellor Signed-off-by: Sasha Levin --- scripts/mod/modpost.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index cfcf2c1bb5ece..41e40c9d3108d 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1730,8 +1730,17 @@ void __attribute__((format(printf, 2, 3))) buf_printf(struct buffer *buf, va_start(ap, fmt); len = vsnprintf(tmp, SZ, fmt, ap); - buf_write(buf, tmp, len); va_end(ap); + + if (len < 0) { + perror("vsnprintf failed"); + exit(1); + } + if (len >= SZ) + fatal("buf_printf output truncated for string %s: %d bytes needed, %d available\n", + tmp, len + 1, SZ); + + buf_write(buf, tmp, len); } void buf_write(struct buffer *buf, const char *s, int len) -- 2.53.0