From: Filipe Manana <fdmanana@xxxxxxxx>
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@xxxxxxxxxxxxxx>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216908
Link: https://lore.kernel.org/linux-btrfs/7f25442f-b121-2a3a-5a3d-22bcaae83cd4@xxxxxxxxxxxxx/
CC: stable@xxxxxxxxxxxxxxx # 6.1
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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.
