[PATCH 3.16 120/192] ext3: preserve i_mode if ext2_set_acl() fails

Ben Hutchings
2017-10-09T13:12:21Z

From: Ben Hutchings <ben@decadent.org.uk>

Based on Ernesto A. Fernández's fix for ext2 (commit fe26569eb919), from
which the following description is taken:

> When changing a file's acl mask, ext2_set_acl() will first set the group
> bits of i_mode to the value of the mask, and only then set the actual
> extended attribute representing the new acl.
>
> If the second part fails (due to lack of space, for example) and the file
> had no acl attribute to begin with, the system will from now on assume
> that the mask permission bits are actual group permission bits, potentially
> granting access to the wrong users.
>
> Prevent this by only changing the inode mode after the acl has been set.

Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ext3/acl.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/fs/ext3/acl.c
+++ b/fs/ext3/acl.c
@@ -227,19 +227,25 @@ ext3_set_acl(struct inode *inode, struct
{
handle_t *handle;
int error, retries = 0;
+ int update_mode = 0;
+ umode_t mode = inode->i_mode;

retry:
handle = ext3_journal_start(inode, EXT3_DATA_TRANS_BLOCKS(inode->i_sb));
if (IS_ERR(handle))
return PTR_ERR(handle);
if (type == ACL_TYPE_ACCESS && acl) {
- error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+ error = posix_acl_update_mode(inode, &mode, &acl);
if (error)
goto journal_stop;
+ update_mode = 1;
+ }
+ error = __ext3_set_acl(handle, inode, type, acl);
+ if (!error && update_mode) {
+ inode->i_mode = mode;
inode->i_ctime = CURRENT_TIME_SEC;
ext3_mark_inode_dirty(handle, inode);
}
- error = __ext3_set_acl(handle, inode, type, acl);
journal_stop:
ext3_journal_stop(handle);
if (error == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))