This is a note to let you know that I've just added the patch titled
fs/file: fix the check in find_next_fd()
to the 4.19-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:
fs-file-fix-the-check-in-find_next_fd.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0899744903b07aaed992314e3faf236e96c9d5a6
Author: Yuntao Wang <yuntao.wang@xxxxxxxxx>
Date: Thu May 30 00:06:56 2024 +0800
fs/file: fix the check in find_next_fd()
[ Upstream commit ed8c7fbdfe117abbef81f65428ba263118ef298a ]
The maximum possible return value of find_next_zero_bit(fdt->full_fds_bits,
maxbit, bitbit) is maxbit. This return value, multiplied by BITS_PER_LONG,
gives the value of bitbit, which can never be greater than maxfd, it can
only be equal to maxfd at most, so the following check 'if (bitbit > maxfd)'
will never be true.
Moreover, when bitbit equals maxfd, it indicates that there are no unused
fds, and the function can directly return.
Fix this check.
Signed-off-by: Yuntao Wang <yuntao.wang@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240529160656.209352-1-yuntao.wang@xxxxxxxxx
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/file.c b/fs/file.c
index 928ba7b8df1e9..f5ba0e6f1a4c6 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -462,12 +462,12 @@ struct files_struct init_files = {
static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
{
- unsigned int maxfd = fdt->max_fds;
+ unsigned int maxfd = fdt->max_fds; /* always multiple of BITS_PER_LONG */
unsigned int maxbit = maxfd / BITS_PER_LONG;
unsigned int bitbit = start / BITS_PER_LONG;
bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
- if (bitbit > maxfd)
+ if (bitbit >= maxfd)
return maxfd;
if (bitbit > start)
start = bitbit;
