Currently a reference to inode->i_mode is passed directly to
posix_acl_update_mode when setting an ACL which results in the inode's
mode always being changed. In case of errors (e.g. in do_set_acl or
even starting a transaction) the old mode needs to be re-assigned to
->i_mode. This mode recovery is done only in case do_set_acl fails,
which leads to buggy behavior in case btrfs_start_transaction fails.
Fix it by simply setting the new mode to a temporary variable which is
assigned to inode->i_mode's only when do_set_acl succeeds. This covers
both failure cases explained above.
Fixes: db0f220e98eb ("btrfs: start transaction in btrfs_set_acl")
Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
---
Changes since v1:
* Eliminated unrealted newline change (Johannes)
* Fixed logic of when i_mode is set, v1 was causing an uninitialised mode
to be assigned to inode->i_mode resulting in fs consistency problems. Fix this
by introducing a variable which is set to true when the i_mode needs to be
changed. I know this variable could be eliminated by simply initialising
mode = inode->i_mode and always assigning it in the if (!ret) branch but I
find this somewhat subtle and rather be explicit with the boolean variable.
fs/btrfs/acl.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index b722866e1442..ac12a4530540 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -112,14 +112,16 @@ static int do_set_acl(struct btrfs_trans_handle *trans, struct inode *inode,
int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
{
int ret;
- umode_t old_mode = inode->i_mode;
+ umode_t mode;
+ bool change_mode = false;
struct btrfs_trans_handle *trans;
struct btrfs_root *root = BTRFS_I(inode)->root;
if (type == ACL_TYPE_ACCESS && acl) {
- ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+ ret = posix_acl_update_mode(inode, &mode, &acl);
if (ret)
return ret;
+ change_mode = true;
}
trans = btrfs_start_transaction(root, 2);
@@ -127,9 +129,9 @@ int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
return PTR_ERR(trans);
ret = do_set_acl(trans, inode, acl, type);
- if (ret) {
- inode->i_mode = old_mode;
- } else {
+ if (!ret) {
+ if (change_mode)
+ inode->i_mode = mode;
inode_inc_iversion(inode);
inode->i_ctime = current_time(inode);
set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
--
2.17.1
