From: Filipe Manana fdmanana@suse.com
commit 1f55ee6d0901d915801618bda0af4e5b937e3db7 upstream.
During lseek, for SEEK_DATA and SEEK_HOLE modes, we access the disk_bytenr of an extent without checking its type. However inline extents have their data starting the offset of the disk_bytenr field, so accessing that field when we have an inline extent can result in either of the following:
1) Interpret the inline extent's data as a disk_bytenr value;
2) In case the inline data is less than 8 bytes, we access part of some other item in the leaf, or unused space in the leaf;
3) In case the inline data is less than 8 bytes and the extent item is the first item in the leaf, we can access beyond the leaf's limit.
So fix this by not accessing the disk_bytenr field if we have an inline extent.
Fixes: b6e833567ea1 ("btrfs: make hole and data seeking a lot more efficient") Reported-by: Matthias Schoepfer matthias.schoepfer@googlemail.com Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216908 Link: https://lore.kernel.org/linux-btrfs/7f25442f-b121-2a3a-5a3d-22bcaae83cd4@lee... CC: stable@vger.kernel.org # 6.1 Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/file.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
--- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -3838,6 +3838,7 @@ static loff_t find_desired_extent(struct struct extent_buffer *leaf = path->nodes[0]; struct btrfs_file_extent_item *extent; u64 extent_end; + u8 type;
if (path->slots[0] >= btrfs_header_nritems(leaf)) { ret = btrfs_next_leaf(root, path); @@ -3892,10 +3893,16 @@ static loff_t find_desired_extent(struct
extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item); + type = btrfs_file_extent_type(leaf, extent);
- if (btrfs_file_extent_disk_bytenr(leaf, extent) == 0 || - btrfs_file_extent_type(leaf, extent) == - BTRFS_FILE_EXTENT_PREALLOC) { + /* + * Can't access the extent's disk_bytenr field if this is an + * inline extent, since at that offset, it's where the extent + * data starts. + */ + if (type == BTRFS_FILE_EXTENT_PREALLOC || + (type == BTRFS_FILE_EXTENT_REG && + btrfs_file_extent_disk_bytenr(leaf, extent) == 0)) { /* * Explicit hole or prealloc extent, search for delalloc. * A prealloc extent is treated like a hole.