ksmbd: fix slab out of bounds write in smb_inherit_dacl()

slab out-of-bounds write is caused by that offsets is bigger than pntsd
allocation size. This patch add the check to validate 3 offsets using
allocation size.

Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-22271
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index 6c0305be895e56fb11464c5fe17245afc4354447..51b8bfab74813fb3f79bc85e2155eeebd84f2d79 100644 (file)
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -1107,6 +1107,7 @@ pass:
                struct smb_acl *pdacl;
                struct smb_sid *powner_sid = NULL, *pgroup_sid = NULL;
                int powner_sid_size = 0, pgroup_sid_size = 0, pntsd_size;
+               int pntsd_alloc_size;
 
                if (parent_pntsd->osidoffset) {
                        powner_sid = (struct smb_sid *)((char *)parent_pntsd +
@@ -1119,9 +1120,10 @@ pass:
                        pgroup_sid_size = 1 + 1 + 6 + (pgroup_sid->num_subauth * 4);
                }
 
-               pntsd = kzalloc(sizeof(struct smb_ntsd) + powner_sid_size +
-                               pgroup_sid_size + sizeof(struct smb_acl) +
-                               nt_size, GFP_KERNEL);
+               pntsd_alloc_size = sizeof(struct smb_ntsd) + powner_sid_size +
+                       pgroup_sid_size + sizeof(struct smb_acl) + nt_size;
+
+               pntsd = kzalloc(pntsd_alloc_size, GFP_KERNEL);
                if (!pntsd) {
                        rc = -ENOMEM;
                        goto free_aces_base;
@@ -1136,6 +1138,27 @@ pass:
                pntsd->gsidoffset = parent_pntsd->gsidoffset;
                pntsd->dacloffset = parent_pntsd->dacloffset;
 
+               if ((u64)le32_to_cpu(pntsd->osidoffset) + powner_sid_size >
+                   pntsd_alloc_size) {
+                       rc = -EINVAL;
+                       kfree(pntsd);
+                       goto free_aces_base;
+               }
+
+               if ((u64)le32_to_cpu(pntsd->gsidoffset) + pgroup_sid_size >
+                   pntsd_alloc_size) {
+                       rc = -EINVAL;
+                       kfree(pntsd);
+                       goto free_aces_base;
+               }
+
+               if ((u64)le32_to_cpu(pntsd->dacloffset) + sizeof(struct smb_acl) + nt_size >
+                   pntsd_alloc_size) {
+                       rc = -EINVAL;
+                       kfree(pntsd);
+                       goto free_aces_base;
+               }
+
                if (pntsd->osidoffset) {
                        struct smb_sid *owner_sid = (struct smb_sid *)((char *)pntsd +
                                        le32_to_cpu(pntsd->osidoffset));