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

[Dmitry Monakhov]

Stanislav Kinsburskiy <skinsbursky at virtuozzo.com> writes:

> 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
ACK.
>
> 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;
>  }
>  
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