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Message-ID: <20240623134548.810179-1-sashal@kernel.org>
Date: Sun, 23 Jun 2024 09:45:46 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: Yuntao Wang <yuntao.wang@...ux.dev>,
Jan Kara <jack@...e.cz>,
Christian Brauner <brauner@...nel.org>,
Sasha Levin <sashal@...nel.org>,
viro@...iv.linux.org.uk,
linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 1/2] fs/file: fix the check in find_next_fd()
From: Yuntao Wang <yuntao.wang@...ux.dev>
[ 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@...ux.dev>
Link: https://lore.kernel.org/r/20240529160656.209352-1-yuntao.wang@linux.dev
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
fs/file.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/file.c b/fs/file.c
index e56059fa1b309..64892b7444191 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;
--
2.43.0
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