[Devel] [PATCH] ext4: release leaked posix acl in ext4_acl_chmod

[Stanislav Kinsburskiy]

Note: only rh7-3.10.0-693.17.1.el7-based kernels are affected.
I.e. starting from rh7-3.10.0-693.17.1.vz7.43.1.

Posix acl is used to convert of an extended attribute, provided by user to
ext4 attributes. In particular to i_mode in case of ACL_TYPE_ACCESS
request.
IOW, this object is allocated, used for convertion, not stored anywhere
and
must be freed.
However posix_acl_update_mode() can zerofy the pointer to support
ext4_set_acl() logic, but then the object is leaked.
So, fix it by releasing new temporary pointer with the same value instead
of
acl pointer.

In scope of https://jira.sw.ru/browse/PSBM-81384

RHEL bug URL: https://bugzilla.redhat.com/show_bug.cgi?id=1543020

Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
---
 fs/ext4/acl.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index f8a38a2..046b338 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -297,7 +297,7 @@ ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
 int
 ext4_acl_chmod(struct inode *inode)
 {
-	struct posix_acl *acl;
+	struct posix_acl *acl, *real_acl;
 	handle_t *handle;
 	int retries = 0;
 	int error;
@@ -315,6 +315,8 @@ ext4_acl_chmod(struct inode *inode)
 	error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
 	if (error)
 		return error;
+
+	real_acl = acl;
 retry:
 	handle = ext4_journal_start(inode, EXT4_HT_XATTR,
 				    ext4_jbd2_credits_xattr(inode));
@@ -341,7 +343,7 @@ ext4_acl_chmod(struct inode *inode)
 	    ext4_should_retry_alloc(inode->i_sb, &retries))
 		goto retry;
 out:
-	posix_acl_release(acl);
+	posix_acl_release(real_acl);
 	return error;
 }