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author | Eric Biggers <ebiggers@google.com> | 2018-04-12 17:48:09 +0200 |
---|---|---|
committer | Theodore Ts'o <tytso@mit.edu> | 2018-04-12 17:48:09 +0200 |
commit | 349fa7d6e1935f49bf4161c4900711b2989180a9 (patch) | |
tree | c8df82a97c0681357988b5d7611679896727242a /fs/ext4 | |
parent | ext4: force revalidation of directory pointer after seekdir(2) (diff) | |
download | linux-349fa7d6e1935f49bf4161c4900711b2989180a9.tar.xz linux-349fa7d6e1935f49bf4161c4900711b2989180a9.zip |
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')
-rw-r--r-- | fs/ext4/extents.c | 16 |
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; } } |