From: Michael Bommarito <michael.bommarito@gmail.com> mainline inclusion from mainline-v7.1-rc1 commit 0a8cf165566ba55a39fd0f4de172119dd646d39a category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14459 CVE: CVE-2026-31709 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a server-supplied dacloffset and then use the incoming ACL to rebuild the chmod/chown security descriptor. The original fix only checked that the struct smb_acl header fits before reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate header-field OOB read, but the rewrite helpers still walk ACEs based on pdacl->num_aces with no structural validation of the incoming DACL body. A malicious server can return a truncated DACL that still contains a header, claims one or more ACEs, and then drive replace_sids_and_copy_aces() or set_chmod_dacl() past the validated extent while they compare or copy attacker-controlled ACEs. Factor the DACL structural checks into validate_dacl(), extend them to validate each ACE against the DACL bounds, and use the shared validator before the chmod/chown rebuild paths. parse_dacl() reuses the same validator so the read-side parser and write-side rewrite paths agree on what constitutes a well-formed incoming DACL. Fixes: bc3e9dd9d104 ("cifs: Change SIDs in ACEs while transferring file ownership.") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Assisted-by: Codex:gpt-5-4 Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com> Signed-off-by: Steve French <stfrench@microsoft.com> Conflicts: fs/smb/client/cifsacl.c [Commit 62e7dd0a39c2 ("smb: common: change the data type of num_aces to le16") change the data type of num_aces to le16; commit 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for non-scalar types") replace kmalloc with kmalloc_obj.] Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- fs/smb/client/cifsacl.c | 116 +++++++++++++++++++++++++++++----------- 1 file changed, 85 insertions(+), 31 deletions(-) diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c index 7bd29e827c8f..d53923fe33a5 100644 --- a/fs/smb/client/cifsacl.c +++ b/fs/smb/client/cifsacl.c @@ -758,6 +758,77 @@ static void dump_ace(struct smb_ace *pace, char *end_of_acl) } #endif +static int validate_dacl(struct smb_acl *pdacl, char *end_of_acl) +{ + int i, ace_hdr_size, ace_size, min_ace_size; + u16 dacl_size, num_aces; + char *acl_base, *end_of_dacl; + struct smb_ace *pace; + + if (!pdacl) + return 0; + + if (end_of_acl < (char *)pdacl + sizeof(struct smb_acl)) { + cifs_dbg(VFS, "ACL too small to parse DACL\n"); + return -EINVAL; + } + + dacl_size = le16_to_cpu(pdacl->size); + if (dacl_size < sizeof(struct smb_acl) || + end_of_acl < (char *)pdacl + dacl_size) { + cifs_dbg(VFS, "ACL too small to parse DACL\n"); + return -EINVAL; + } + + num_aces = le16_to_cpu(pdacl->num_aces); + if (!num_aces) + return 0; + + ace_hdr_size = offsetof(struct smb_ace, sid) + + offsetof(struct smb_sid, sub_auth); + min_ace_size = ace_hdr_size + sizeof(__le32); + if (num_aces > (dacl_size - sizeof(struct smb_acl)) / min_ace_size) { + cifs_dbg(VFS, "ACL too small to parse DACL\n"); + return -EINVAL; + } + + end_of_dacl = (char *)pdacl + dacl_size; + acl_base = (char *)pdacl; + ace_size = sizeof(struct smb_acl); + + for (i = 0; i < num_aces; ++i) { + if (end_of_dacl - acl_base < ace_size) { + cifs_dbg(VFS, "ACL too small to parse ACE\n"); + return -EINVAL; + } + + pace = (struct smb_ace *)(acl_base + ace_size); + acl_base = (char *)pace; + + if (end_of_dacl - acl_base < ace_hdr_size || + pace->sid.num_subauth == 0 || + pace->sid.num_subauth > SID_MAX_SUB_AUTHORITIES) { + cifs_dbg(VFS, "ACL too small to parse ACE\n"); + return -EINVAL; + } + + ace_size = ace_hdr_size + sizeof(__le32) * pace->sid.num_subauth; + if (end_of_dacl - acl_base < ace_size || + le16_to_cpu(pace->size) < ace_size) { + cifs_dbg(VFS, "ACL too small to parse ACE\n"); + return -EINVAL; + } + + ace_size = le16_to_cpu(pace->size); + if (end_of_dacl - acl_base < ace_size) { + cifs_dbg(VFS, "ACL too small to parse ACE\n"); + return -EINVAL; + } + } + + return 0; +} + static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, struct smb_sid *pownersid, struct smb_sid *pgrpsid, struct cifs_fattr *fattr, bool mode_from_special_sid) @@ -765,7 +836,7 @@ static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, int i; int num_aces = 0; int acl_size; - char *acl_base; + char *acl_base, *end_of_dacl; struct smb_ace **ppace; /* BB need to add parm so we can store the SID BB */ @@ -777,12 +848,8 @@ static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, return; } - /* validate that we do not go past end of acl */ - if (end_of_acl < (char *)pdacl + sizeof(struct smb_acl) || - end_of_acl < (char *)pdacl + le16_to_cpu(pdacl->size)) { - cifs_dbg(VFS, "ACL too small to parse DACL\n"); + if (validate_dacl(pdacl, end_of_acl)) return; - } cifs_dbg(NOISY, "DACL revision %d size %d num aces %d\n", le16_to_cpu(pdacl->revision), le16_to_cpu(pdacl->size), @@ -793,6 +860,7 @@ static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, user/group/other have no permissions */ fattr->cf_mode &= ~(0777); + end_of_dacl = (char *)pdacl + le16_to_cpu(pdacl->size); acl_base = (char *)pdacl; acl_size = sizeof(struct smb_acl); @@ -800,36 +868,16 @@ static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, if (num_aces > 0) { umode_t denied_mode = 0; - if (num_aces > (le16_to_cpu(pdacl->size) - sizeof(struct smb_acl)) / - (offsetof(struct smb_ace, sid) + - offsetof(struct smb_sid, sub_auth) + sizeof(__le16))) - return; - ppace = kmalloc_array(num_aces, sizeof(struct smb_ace *), GFP_KERNEL); if (!ppace) return; for (i = 0; i < num_aces; ++i) { - if (end_of_acl - acl_base < acl_size) - break; - ppace[i] = (struct smb_ace *) (acl_base + acl_size); - acl_base = (char *)ppace[i]; - acl_size = offsetof(struct smb_ace, sid) + - offsetof(struct smb_sid, sub_auth); - - if (end_of_acl - acl_base < acl_size || - ppace[i]->sid.num_subauth == 0 || - ppace[i]->sid.num_subauth > SID_MAX_SUB_AUTHORITIES || - (end_of_acl - acl_base < - acl_size + sizeof(__le32) * ppace[i]->sid.num_subauth) || - (le16_to_cpu(ppace[i]->size) < - acl_size + sizeof(__le32) * ppace[i]->sid.num_subauth)) - break; #ifdef CONFIG_CIFS_DEBUG2 - dump_ace(ppace[i], end_of_acl); + dump_ace(ppace[i], end_of_dacl); #endif if (mode_from_special_sid && (compare_sids(&(ppace[i]->sid), @@ -871,6 +919,7 @@ static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, (void *)ppace[i], sizeof(struct smb_ace)); */ + acl_base = (char *)ppace[i]; acl_size = le16_to_cpu(ppace[i]->size); } @@ -1294,10 +1343,9 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd, dacloffset = le32_to_cpu(pntsd->dacloffset); if (dacloffset) { dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); - if (end_of_acl < (char *)dacl_ptr + le16_to_cpu(dacl_ptr->size)) { - cifs_dbg(VFS, "Server returned illegal ACL size\n"); - return -EINVAL; - } + rc = validate_dacl(dacl_ptr, end_of_acl); + if (rc) + return rc; } owner_sid_ptr = (struct smb_sid *)((char *)pntsd + @@ -1668,6 +1716,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode, dacloffset = le32_to_cpu(pntsd->dacloffset); if (dacloffset) { dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); + rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen); + if (rc) { + kfree(pntsd); + cifs_put_tlink(tlink); + return rc; + } if (mode_from_sid) nsecdesclen += le32_to_cpu(dacl_ptr->num_aces) * sizeof(struct smb_ace); -- 2.52.0