{"id":2223493,"url":"http://patchwork.ozlabs.org/api/1.2/patches/2223493/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-cifs-client/patch/20260415112501.116426-3-michael.bommarito@gmail.com/","project":{"id":12,"url":"http://patchwork.ozlabs.org/api/1.2/projects/12/?format=json","name":"Linux CIFS Client","link_name":"linux-cifs-client","list_id":"linux-cifs.vger.kernel.org","list_email":"linux-cifs@vger.kernel.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260415112501.116426-3-michael.bommarito@gmail.com>","list_archive_url":null,"date":"2026-04-15T11:25:01","name":"[v2,2/2] ksmbd: require minimum ACE size in smb_check_perm_dacl()","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"1a812291c2cf14153c9c673437b1a5c83e8f998d","submitter":{"id":93078,"url":"http://patchwork.ozlabs.org/api/1.2/people/93078/?format=json","name":"Michael Bommarito","email":"michael.bommarito@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-cifs-client/patch/20260415112501.116426-3-michael.bommarito@gmail.com/mbox/","series":[{"id":499975,"url":"http://patchwork.ozlabs.org/api/1.2/series/499975/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-cifs-client/list/?series=499975","date":"2026-04-15T11:24:59","name":"ksmbd: harden ipc_validate_msg() and smb_check_perm_dacl()","version":2,"mbox":"http://patchwork.ozlabs.org/series/499975/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2223493/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2223493/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-cifs@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=diaIpdD7;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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/* upper loop */\n compare_sids(&sid, &ace->sid); /* lower loop */\n\nreads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at\noffset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES\n* 4 bytes).\n\nTighten both loops to require\n\n ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE\n\nwhich is the smallest valid on-wire ACE layout (4-byte header +\n4-byte access_req + 8-byte sid base with zero sub-auths). Also\nreject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES\nbefore letting compare_sids() dereference sub_auth[] entries.\n\nparse_sec_desc() already enforces an equivalent check (lines 441-448);\nsmb_check_perm_dacl() simply grew weaker validation over time.\n\nReachability: authenticated SMB client with permission to set an ACL\non a file. On a subsequent CREATE against that file, the kernel\nwalks the stored DACL via smb_check_perm_dacl() and triggers the\nOOB read. Not pre-auth, and the OOB read is not reflected to the\nattacker, but KASAN reports and kernel state corruption are\npossible.\n\nFixes: e2f34481b24d (\"cifsd: add server-side procedures for SMB3\")\nCc: stable@vger.kernel.org\nAssisted-by: Claude:claude-opus-4-6\nAssisted-by: Codex:gpt-5-4\nSigned-off-by: Michael Bommarito \n---\n fs/smb/server/smbacl.c | 17 +++++++++++++----\n 1 file changed, 13 insertions(+), 4 deletions(-)","diff":"diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c\nindex c30d01877c41..d5943256c071 100644\n--- a/fs/smb/server/smbacl.c\n+++ b/fs/smb/server/smbacl.c\n@@ -1341,10 +1341,13 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,\n \t\tace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));\n \t\taces_size = acl_size - sizeof(struct smb_acl);\n \t\tfor (i = 0; i < le16_to_cpu(pdacl->num_aces); i++) {\n-\t\t\tif (offsetof(struct smb_ace, access_req) > aces_size)\n+\t\t\tif (offsetof(struct smb_ace, sid) +\n+\t\t\t CIFS_SID_BASE_SIZE > aces_size)\n \t\t\t\tbreak;\n \t\t\tace_size = le16_to_cpu(ace->size);\n-\t\t\tif (ace_size > aces_size)\n+\t\t\tif (ace_size > aces_size ||\n+\t\t\t ace_size < offsetof(struct smb_ace, sid) +\n+\t\t\t\t CIFS_SID_BASE_SIZE)\n \t\t\t\tbreak;\n \t\t\taces_size -= ace_size;\n \t\t\tgranted |= le32_to_cpu(ace->access_req);\n@@ -1359,13 +1362,19 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,\n \tace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));\n \taces_size = acl_size - sizeof(struct smb_acl);\n \tfor (i = 0; i < le16_to_cpu(pdacl->num_aces); i++) {\n-\t\tif (offsetof(struct smb_ace, access_req) > aces_size)\n+\t\tif (offsetof(struct smb_ace, sid) +\n+\t\t CIFS_SID_BASE_SIZE > aces_size)\n \t\t\tbreak;\n \t\tace_size = le16_to_cpu(ace->size);\n-\t\tif (ace_size > aces_size)\n+\t\tif (ace_size > aces_size ||\n+\t\t ace_size < offsetof(struct smb_ace, sid) +\n+\t\t\t CIFS_SID_BASE_SIZE)\n \t\t\tbreak;\n \t\taces_size -= ace_size;\n \n+\t\tif (ace->sid.num_subauth > SID_MAX_SUB_AUTHORITIES)\n+\t\t\tbreak;\n+\n \t\tif (!compare_sids(&sid, &ace->sid) ||\n \t\t !compare_sids(&sid_unix_NFS_mode, &ace->sid)) {\n \t\t\tfound = 1;\n","prefixes":["v2","2/2"]}