In mext_replace_branches(), the oext and dext virable might be NULL if the
orig extent and donor extent are empty. Later calling *oext and *dext will
trigger a kernel null pointer bug like this:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffffa0636563>] mext_replace_branches+0x10c/0x2f3 [ext4]
PGD 37dba067 PUD cd8ac067 PMD 0
Oops: 0000 [#1] SMP
The patch checks the two virables and returns EOPNOTSUPP if either of them
is NULL.
Signed-off-by: Peng Tao <bergwolf@xxxxxxxxx>
---
fs/ext4/move_extent.c | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 5821e0b..4923f70 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -641,10 +641,22 @@ mext_replace_branches(handle_t *handle, struct inode *orig_inode,
goto out;
depth = ext_depth(orig_inode);
oext = orig_path[depth].p_ext;
+ if (oext == NULL) {
+ ext4_debug("ext4 move extent: "
+ "orig extents should not be empty\n");
+ err = -EOPNOTSUPP;
+ goto out;
+ }
tmp_oext = *oext;
depth = ext_depth(donor_inode);
dext = donor_path[depth].p_ext;
+ if (dext == NULL) {
+ ext4_debug("ext4 move extent: "
+ "donor extents should not be empty\n");
+ err = -EOPNOTSUPP;
+ goto out;
+ }
tmp_dext = *dext;
mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
--
1.6.2.GIT
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