6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Joanne Koong joannelkoong@gmail.com
[ Upstream commit 9d875e0eef8ec15b6b1da0cb9a0f8ed13efee89e ]
The end position to start truncating from may be at an offset into a block, which under the current logic would result in overtruncation.
Adjust the calculation to account for unaligned end offsets.
Signed-off-by: Joanne Koong joannelkoong@gmail.com Link: https://patch.msgid.link/20251111193658.3495942-3-joannelkoong@gmail.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/iomap/buffered-io.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 13a5f4422c797..7e9480150d61e 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -188,6 +188,22 @@ static void ifs_free(struct folio *folio) kfree(ifs); }
+/* + * Calculate how many bytes to truncate based off the number of blocks to + * truncate and the end position to start truncating from. + */ +static size_t iomap_bytes_to_truncate(loff_t end_pos, unsigned block_bits, + unsigned blocks_truncated) +{ + unsigned block_size = 1 << block_bits; + unsigned block_offset = end_pos & (block_size - 1); + + if (!block_offset) + return blocks_truncated << block_bits; + + return ((blocks_truncated - 1) << block_bits) + block_offset; +} + /* * Calculate the range inside the folio that we actually need to read. */ @@ -233,7 +249,8 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio, /* truncate len if we find any trailing uptodate block(s) */ while (++i <= last) { if (ifs_block_is_uptodate(ifs, i)) { - plen -= (last - i + 1) * block_size; + plen -= iomap_bytes_to_truncate(*pos + plen, + block_bits, last - i + 1); last = i - 1; break; } @@ -249,7 +266,8 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio, unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
if (first <= end && last > end) - plen -= (last - end) * block_size; + plen -= iomap_bytes_to_truncate(*pos + plen, block_bits, + last - end); }
*offp = poff;