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btrfs: fix invalid leaf access due to inline extent during lseek

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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: b6e833567e ("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/
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>
This commit is contained in:
Filipe Manana 2023-01-12 14:17:20 +00:00 committed by David Sterba
parent 26ecf243e4
commit 1f55ee6d09
1 changed files with 10 additions and 3 deletions
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13
fs/btrfs/file.c
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@ -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.