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author | Eric Biggers <ebiggers@google.com> | 2018-04-12 11:48:09 -0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-01 15:13:03 -0700 |
commit | a405a2a02793b217b4402ab898f877dac4db7e66 (patch) | |
tree | e67a823fb76d7bbe33fb375d6cd2c2869c12465f /fs/ext4/extents.c | |
parent | ba3cd5796223e0971d30e910e0d5b953576f8629 (diff) | |
download | linux-stable-a405a2a02793b217b4402ab898f877dac4db7e66.tar.gz linux-stable-a405a2a02793b217b4402ab898f877dac4db7e66.tar.bz2 linux-stable-a405a2a02793b217b4402ab898f877dac4db7e66.zip |
ext4: prevent right-shifting extents beyond EXT_MAX_BLOCKS
commit 349fa7d6e1935f49bf4161c4900711b2989180a9 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/ext4/extents.c')
-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 1a0c57100f28..63c702b4b24c 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -5356,8 +5356,9 @@ 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, @@ -5377,9 +5378,14 @@ 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; } } |