From: Joanne Koong [ Upstream commit 7aa6bc3e8766990824f66ca76c19596ce10daf3e ] iomap_adjust_read_range() assumes that the position and length passed in are block-aligned. This is not always the case however, as shown in the syzbot generated case for erofs. This causes too many bytes to be skipped for uptodate blocks, which results in returning the incorrect position and length to read in. If all the blocks are uptodate, this underflows length and returns a position beyond the folio. Fix the calculation to also take into account the block offset when calculating how many bytes can be skipped for uptodate blocks. Signed-off-by: Joanne Koong Tested-by: syzbot@syzkaller.appspotmail.com Reviewed-by: Brian Foster Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin Signed-off-by: Miguel Gazquez (Schneider Electric) --- fs/iomap/buffered-io.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 219f9e1a2643..5ad3bf906b35 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -103,17 +103,24 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop, * to avoid reading in already uptodate ranges. */ if (iop) { - unsigned int i; + unsigned int i, blocks_skipped; /* move forward for each leading block marked uptodate */ - for (i = first; i <= last; i++) { + for (i = first; i <= last; i++) if (!test_bit(i, iop->uptodate)) break; - *pos += block_size; - poff += block_size; - plen -= block_size; - first++; + + blocks_skipped = i - first; + if (blocks_skipped) { + unsigned long block_offset = *pos & (block_size - 1); + unsigned bytes_skipped = + (blocks_skipped << block_bits) - block_offset; + + *pos += bytes_skipped; + poff += bytes_skipped; + plen -= bytes_skipped; } + first = i; /* truncate len if we find any trailing uptodate block(s) */ for ( ; i <= last; i++) { --- base-commit: 2a3da1f4966798b0b48ce302944ad356b2c98b5d change-id: 20260820-cve-2025-68974-5-10-de7bb9adcd01 Best regards, -- Miguel Gazquez (Schneider Electric)