6.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paul Moore <paul@xxxxxxxxxxxxxx>
[ Upstream commit eaf0e7a3d2711018789e9fdb89191d19aa139c47 ]
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 d7cf3412a9f6
("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@xxxxxxxxxxxxxxx
Fixes: d7cf3412a9f6 ("lsm: consolidate buffer size handling into lsm_fill_user_ctx()")
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
security/security.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/security/security.c b/security/security.c
index fb7505c734853..a344b8fa5530d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -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;
--
2.43.0
