4.19-stable review patch. If anyone has any objections, please let me know.
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From: Yuntao Wang yuntao.wang@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@linux.dev Link: https://lore.kernel.org/r/20240529160656.209352-1-yuntao.wang@linux.dev Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/file.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
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;