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authorEric Biggers <ebiggers@google.com>2018-04-12 11:48:09 -0400
committerTheodore Ts'o <tytso@mit.edu>2018-04-12 11:48:09 -0400
commit349fa7d6e1935f49bf4161c4900711b2989180a9 (patch)
treec8df82a97c0681357988b5d7611679896727242a /fs/ext4/extents.c
parente40ff213898502d299351cc2fe1e350cd186f0d3 (diff)
ext4: prevent right-shifting extents beyond EXT_MAX_BLOCKS
During the "insert range" fallocate operation, extents starting at the range offset are shifted "right" (to a higher file offset) by the range length. But, as shown by syzbot, it's not validated that this doesn't cause extents to be shifted beyond EXT_MAX_BLOCKS. In that case ->ee_block can wrap around, corrupting the extent tree. Fix it by returning an error if the space between the end of the last extent and EXT4_MAX_BLOCKS is smaller than the range being inserted. This bug can be reproduced by running the following commands when the current directory is on an ext4 filesystem with a 4k block size: fallocate -l 8192 file fallocate --keep-size -o 0xfffffffe000 -l 4096 -n file fallocate --insert-range -l 8192 file Then after unmounting the filesystem, e2fsck reports corruption. Reported-by: syzbot+06c885be0edcdaeab40c@syzkaller.appspotmail.com Fixes: 331573febb6a ("ext4: Add support FALLOC_FL_INSERT_RANGE for fallocate") Cc: stable@vger.kernel.org # v4.2+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/extents.c')
-rw-r--r--fs/ext4/extents.c16
1 files changed, 11 insertions, 5 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 0a7315961bac..c969275ce3ee 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5329,8 +5329,9 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
stop = le32_to_cpu(extent->ee_block);
/*
- * In case of left shift, Don't start shifting extents until we make
- * sure the hole is big enough to accommodate the shift.
+ * For left shifts, make sure the hole on the left is big enough to
+ * accommodate the shift. For right shifts, make sure the last extent
+ * won't be shifted beyond EXT_MAX_BLOCKS.
*/
if (SHIFT == SHIFT_LEFT) {
path = ext4_find_extent(inode, start - 1, &path,
@@ -5350,9 +5351,14 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle,
if ((start == ex_start && shift > ex_start) ||
(shift > start - ex_end)) {
- ext4_ext_drop_refs(path);
- kfree(path);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
+ }
+ } else {
+ if (shift > EXT_MAX_BLOCKS -
+ (stop + ext4_ext_get_actual_len(extent))) {
+ ret = -EINVAL;
+ goto out;
}
}