Commit eaf0e7a3 authored by Paul Moore's avatar Paul Moore
Browse files

lsm: handle the NULL buffer case in lsm_fill_user_ctx() 



Passing a NULL buffer into the lsm_get_self_attr() syscall is a valid
way to quickly determine the minimum size of the buffer needed to for
the syscall to return all of the LSM attributes to the caller.
Unfortunately we/I broke that behavior in commit d7cf3412
("lsm: consolidate buffer size handling into lsm_fill_user_ctx()")
such that it returned an error to the caller; this patch restores the
original desired behavior of using the NULL buffer as a quick way to
correctly size the attribute buffer.

Cc: stable@vger.kernel.org
Fixes: d7cf3412 ("lsm: consolidate buffer size handling into lsm_fill_user_ctx()")
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent a5a858f6

security/security.c

+7 −1
Original line number Diff line number Diff line
@@ -780,7 +780,9 @@ static int lsm_superblock_alloc(struct super_block *sb) 
 * @id: LSM id

 * @flags: LSM defined flags

 *

 * Fill all of the fields in a userspace lsm_ctx structure.

 * Fill all of the fields in a userspace lsm_ctx structure.  If @uctx is NULL

 * simply calculate the required size to output via @utc_len and return

 * success.

 *

 * Returns 0 on success, -E2BIG if userspace buffer is not large enough,

 * -EFAULT on a copyout error, -ENOMEM if memory can't be allocated.
@@ -799,6 +801,10 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len, 
		goto out;

	}



	/* no buffer - return success/0 and set @uctx_len to the req size */

	if (!uctx)

		goto out;



	nctx = kzalloc(nctx_len, GFP_KERNEL);

	if (nctx == NULL) {

		rc = -ENOMEM;