[PATCH AUTOSEL 6.6 08/16] fs/file: fix the check in find_next_fd()

[PATCH AUTOSEL 6.6 08/16] fs/file: fix the check in find_next_fd()

[Sasha Levin]

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 3e4a4dfa38fca..a815f6eddc511 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

[PATCH AUTOSEL 6.6 11/16] iomap: Fix iomap_adjust_read_range for plen calculation

[Sasha Levin]

From: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>

[ Upstream commit f5ceb1bbc98c69536d4673a97315e8427e67de1b ]

If the extent spans the block that contains i_size, we need to handle
both halves separately so that we properly zero data in the page cache
for blocks that are entirely outside of i_size. But this is needed only
when i_size is within the current folio under processing.
"orig_pos + length > isize" can be true for all folios if the mapped
extent length is greater than the folio size. That is making plen to
break for every folio instead of only the last folio.

So use orig_plen for checking if "orig_pos + orig_plen > isize".

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/a32e5f9a4fcfdb99077300c4020ed7ae61d6e0f9.1715067055.git.ritesh.list@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
cc: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/iomap/buffered-io.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 129a85633797a..975fd88c1f0f4 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -201,6 +201,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 	unsigned block_size = (1 << block_bits);
 	size_t poff = offset_in_folio(folio, *pos);
 	size_t plen = min_t(loff_t, folio_size(folio) - poff, length);
+	size_t orig_plen = plen;
 	unsigned first = poff >> block_bits;
 	unsigned last = (poff + plen - 1) >> block_bits;
 
@@ -237,7 +238,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 	 * handle both halves separately so that we properly zero data in the
 	 * page cache for blocks that are entirely outside of i_size.
 	 */
-	if (orig_pos <= isize && orig_pos + length > isize) {
+	if (orig_pos <= isize && orig_pos + orig_plen > isize) {
 		unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
 
 		if (first <= end && last > end)
-- 
2.43.0