fs/select.c: fix information leak to userspace

On some architectures __kernel_suseconds_t is int.  On these archs struct
timeval has padding bytes at the end.  This struct is copied to userspace
with these padding bytes uninitialized.  This leads to leaking of contents
of kernel stack memory.

This bug was added with v2.6.27-rc5-286-gb773ad4.

[akpm@linux-foundation.org: avoid the memset on architectures which don't need it]
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/select.c b/fs/select.c
index 500a669f779016eb33a4e570805285d6d44e7af2..a8e5ab2014ea294c57a4e906f73430b5f4402932 100644 (file)
--- a/fs/select.c
+++ b/fs/select.c
@@ -306,6 +306,8 @@ static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
                rts.tv_sec = rts.tv_nsec = 0;
 
        if (timeval) {
+               if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
+                       memset(&rtv, 0, sizeof(rtv));
                rtv.tv_sec = rts.tv_sec;
                rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;