| Message ID | 860221a4cf1642689ed17404c12b920d1acf1019.1673532966.git.fdmanana@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: fix invalid leaf access due to inline extent during lseek | expand |
On Thu, Jan 12, 2023 at 02:17:20PM +0000, fdmanana@kernel.org wrote: > From: Filipe Manana <fdmanana@suse.com> > > During lseek, for SEEK_DATA and SEEK_HOLE modes, we access the disk_bytenr > of anextent 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@leemhuis.info/ > Signed-off-by: Filipe Manana <fdmanana@suse.com> Added to misc-next, thanks.
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 834bbcb91102..af046d22300e 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -3541,6 +3541,7 @@ static loff_t find_desired_extent(struct file *file, loff_t offset, int whence) 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); @@ -3596,10 +3597,16 @@ static loff_t find_desired_extent(struct file *file, loff_t offset, int whence) 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.