From: Yuntao Wang <yuntao.wang(a)linux.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(a)linux.dev>
Link: https://lore.kernel.org/r/20240529160656.209352-1-yuntao.wang@linux.dev
Reviewed-by: Jan Kara <jack(a)suse.cz>
Signed-off-by: Christian Brauner <brauner(a)kernel.org>
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
fs/file.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/file.c b/fs/file.c
index 69a51d37b66d9..b46a4a725a0ef 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -481,12 +481,12 @@ 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