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authorFilipe Manana <fdmanana@suse.com>2023-01-12 14:17:20 +0000
committerDavid Sterba <dsterba@suse.com>2023-01-16 19:46:38 +0100
commit1f55ee6d0901d915801618bda0af4e5b937e3db7 (patch)
tree5b586ab7e4951c99b0d65173ac3df49d856e68fc
parent26ecf243e407be54807ad67210f7e83b9fad71ea (diff)
btrfs: fix invalid leaf access due to inline extent during lseek
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@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>
-rw-r--r--fs/btrfs/file.c13
1 files changed, 10 insertions, 3 deletions
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.