7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Namjae Jeon commit 3474e1a304fbf9f7c996b24adcd519e031227a90 upstream. parse_sec_desc() constructs SID and DACL pointers by adding untrusted 32-bit offsets to the security descriptor before checking their bounds. The existing checks reject offsets into the descriptor header, but do not reject offsets beyond the descriptor's length. On a 32-bit kernel, a large offset can wrap the pointer before the descriptor. The end-only checks in parse_sid() and parse_dacl() can then accept it, allowing an authenticated SMB2 SET_INFO request to access memory outside the security descriptor and fault the kernel. Check each nonzero offset against acl_len before constructing its pointer. Initialize the optional owner and group SID pointers to NULL so an omitted SID remains absent when parsing the DACL. Fixes: 0626e6641f6b ("cifsd: add server handler for central processing and tranport layers") Cc: stable@vger.kernel.org Reported-by: Ratnaker Gautam Signed-off-by: Namjae Jeon Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smbacl.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -899,7 +899,7 @@ int parse_sec_desc(struct mnt_idmap *idm int acl_len, struct smb_fattr *fattr) { int rc = 0; - struct smb_sid *owner_sid_ptr, *group_sid_ptr; + struct smb_sid *owner_sid_ptr = NULL, *group_sid_ptr = NULL; struct smb_acl *dacl_ptr; /* no need for SACL ptr */ char *end_of_acl = ((char *)pntsd) + acl_len; __u32 dacloffset; @@ -911,12 +911,7 @@ int parse_sec_desc(struct mnt_idmap *idm if (acl_len < sizeof(struct smb_ntsd)) return -EINVAL; - owner_sid_ptr = (struct smb_sid *)((char *)pntsd + - le32_to_cpu(pntsd->osidoffset)); - group_sid_ptr = (struct smb_sid *)((char *)pntsd + - le32_to_cpu(pntsd->gsidoffset)); dacloffset = le32_to_cpu(pntsd->dacloffset); - dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); ksmbd_debug(SMB, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n", pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset), @@ -932,9 +927,12 @@ int parse_sec_desc(struct mnt_idmap *idm pntsd->type = cpu_to_le16(DACL_PRESENT); if (pntsd->osidoffset) { - if (le32_to_cpu(pntsd->osidoffset) < sizeof(struct smb_ntsd)) + if (le32_to_cpu(pntsd->osidoffset) < sizeof(struct smb_ntsd) || + le32_to_cpu(pntsd->osidoffset) >= acl_len) return -EINVAL; + owner_sid_ptr = (struct smb_sid *)((char *)pntsd + + le32_to_cpu(pntsd->osidoffset)); rc = parse_sid(owner_sid_ptr, end_of_acl); if (rc) { pr_err("%s: Error %d parsing Owner SID\n", __func__, rc); @@ -950,9 +948,12 @@ int parse_sec_desc(struct mnt_idmap *idm } if (pntsd->gsidoffset) { - if (le32_to_cpu(pntsd->gsidoffset) < sizeof(struct smb_ntsd)) + if (le32_to_cpu(pntsd->gsidoffset) < sizeof(struct smb_ntsd) || + le32_to_cpu(pntsd->gsidoffset) >= acl_len) return -EINVAL; + group_sid_ptr = (struct smb_sid *)((char *)pntsd + + le32_to_cpu(pntsd->gsidoffset)); rc = parse_sid(group_sid_ptr, end_of_acl); if (rc) { pr_err("%s: Error %d mapping Owner SID to gid\n", @@ -974,9 +975,10 @@ int parse_sec_desc(struct mnt_idmap *idm pntsd->type |= cpu_to_le16(DACL_PROTECTED); if (dacloffset) { - if (dacloffset < sizeof(struct smb_ntsd)) + if (dacloffset < sizeof(struct smb_ntsd) || dacloffset >= acl_len) return -EINVAL; + dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); rc = parse_dacl(idmap, dacl_ptr, end_of_acl, owner_sid_ptr, group_sid_ptr, fattr); if (rc)