From: Greg KH <greg@kroah.com>
To: Sasha Levin <sashal@kernel.org>
Cc: stable@vger.kernel.org, Paulo Alcantara <pc@manguebit.org>,
Namjae Jeon <linkinjeon@kernel.org>,
Ronnie Sahlberg <ronniesahlberg@gmail.com>,
Shyam Prasad N <sprasad@microsoft.com>,
Tom Talpey <tom@talpey.com>, Bharath SM <bharathsm@microsoft.com>
Subject: Re: [PATCH 6.18.y 2/2] smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid
Date: Thu, 17 Sep 2026 11:11:44 +0100 [thread overview]
Message-ID: <2026091740-corner-pantry-5439@gregkh> (raw)
In-Reply-To: <20260917042310.31062-2-sashal@kernel.org>
On Thu, Sep 17, 2026 at 12:23:10AM -0400, Sasha Levin wrote:
> From: Paulo Alcantara <pc@manguebit.org>
>
> [ Upstream commit 18a72975e9f35aadecc75b031f693f2d1f49308f ]
>
> When the administrator mounts with forceuid or forcegid (uid=/gid=
> mount options), they expect all files to appear owned by the specified
> user/group. However, several code paths unconditionally called
> sid_to_id() to overwrite cf_uid/cf_gid with server-provided values,
> ignoring the administrator's explicit override:
>
> - smb311_posix_info_to_fattr() (stat via POSIX extensions)
> - cifs_posix_to_fattr() (readdir via POSIX extensions)
> - parse_sec_desc() (CIFS ACL ownership mapping)
>
> This allowed an untrusted server to dictate local file ownership even
> when the mount was configured to force specific uid/gid values.
>
> Fix all three call sites to check CIFS_MOUNT_OVERR_UID and
> CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the
> same pattern already used by cifs_unix_basic_to_fattr() for unix
> extensions.
>
> Closes: https://sashiko.dev/#/patchset/20260906155816.603278-1-pc%40manguebit.org
> Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> fs/smb/client/cifsacl.c | 29 ++++++++++++++++++-----------
> fs/smb/client/inode.c | 9 +++++++--
> fs/smb/client/readdir.c | 9 +++++++--
> 3 files changed, 32 insertions(+), 15 deletions(-)
>
> diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
> index 11268d10a70ed..c66bbd5606a16 100644
> --- a/fs/smb/client/cifsacl.c
> +++ b/fs/smb/client/cifsacl.c
> @@ -1299,6 +1299,7 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
> {
> int rc = 0;
> struct smb_sid *owner_sid_ptr, *group_sid_ptr;
> + unsigned int sbflags = cifs_sb_flags(cifs_sb);
> struct smb_acl *dacl_ptr; /* no need for SACL ptr */
> char *end_of_acl;
> __u32 dacloffset, osidoffset, gsidoffset;
> @@ -1317,17 +1318,21 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
> cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
> pntsd->revision, pntsd->type, osidoffset, gsidoffset,
> le32_to_cpu(pntsd->sacloffset), dacloffset);
> -/* cifs_dump_mem("owner_sid: ", owner_sid_ptr, 64); */
> + fattr->cf_uid = cifs_sb->ctx->linux_uid;
> + fattr->cf_gid = cifs_sb->ctx->linux_gid;
> +
> rc = sid_from_sd(pntsd, acl_len, osidoffset, &owner_sid_ptr);
> if (rc) {
> cifs_dbg(FYI, "%s: Error %d parsing Owner SID\n", __func__, rc);
> return rc;
> }
> - rc = sid_to_id(cifs_sb, owner_sid_ptr, fattr, SIDOWNER);
> - if (rc) {
> - cifs_dbg(FYI, "%s: Error %d mapping Owner SID to uid\n",
> - __func__, rc);
> - return rc;
> + if (!(sbflags & CIFS_MOUNT_OVERR_UID)) {
> + rc = sid_to_id(cifs_sb, owner_sid_ptr, fattr, SIDOWNER);
> + if (rc) {
> + cifs_dbg(FYI, "%s: Error %d mapping Owner SID to uid\n",
> + __func__, rc);
> + return rc;
> + }
> }
>
> rc = sid_from_sd(pntsd, acl_len, gsidoffset, &group_sid_ptr);
> @@ -1336,11 +1341,13 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
> __func__, rc);
> return rc;
> }
> - rc = sid_to_id(cifs_sb, group_sid_ptr, fattr, SIDGROUP);
> - if (rc) {
> - cifs_dbg(FYI, "%s: Error %d mapping Group SID to gid\n",
> - __func__, rc);
> - return rc;
> + if (!(sbflags & CIFS_MOUNT_OVERR_GID)) {
> + rc = sid_to_id(cifs_sb, group_sid_ptr, fattr, SIDGROUP);
> + if (rc) {
> + cifs_dbg(FYI, "%s: Error %d mapping Group SID to gid\n",
> + __func__, rc);
> + return rc;
> + }
> }
>
> if (dacloffset) {
> diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
> index f23c36d6ae6b3..f2adac6df7b24 100644
> --- a/fs/smb/client/inode.c
> +++ b/fs/smb/client/inode.c
> @@ -847,6 +847,7 @@ static void smb311_posix_info_to_fattr(struct cifs_fattr *fattr,
> struct smb311_posix_qinfo *info = &data->posix_fi;
> struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
> struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
> + unsigned int sbflags = cifs_sb_flags(cifs_sb);
>
> memset(fattr, 0, sizeof(*fattr));
>
> @@ -891,8 +892,12 @@ static void smb311_posix_info_to_fattr(struct cifs_fattr *fattr,
> fattr->cf_symlink_target = data->symlink_target;
> data->symlink_target = NULL;
> }
> - sid_to_id(cifs_sb, &data->posix_owner, fattr, SIDOWNER);
> - sid_to_id(cifs_sb, &data->posix_group, fattr, SIDGROUP);
> + fattr->cf_uid = cifs_sb->ctx->linux_uid;
> + fattr->cf_gid = cifs_sb->ctx->linux_gid;
> + if (!(sbflags & CIFS_MOUNT_OVERR_UID))
> + sid_to_id(cifs_sb, &data->posix_owner, fattr, SIDOWNER);
> + if (!(sbflags & CIFS_MOUNT_OVERR_GID))
> + sid_to_id(cifs_sb, &data->posix_group, fattr, SIDGROUP);
>
> cifs_dbg(FYI, "POSIX query info: mode 0x%x uniqueid 0x%llx nlink %d\n",
> fattr->cf_mode, fattr->cf_uniqueid, fattr->cf_nlink);
> diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
> index f0ce26622a140..93135be123316 100644
> --- a/fs/smb/client/readdir.c
> +++ b/fs/smb/client/readdir.c
> @@ -242,6 +242,7 @@ static void
> cifs_posix_to_fattr(struct cifs_fattr *fattr, struct smb2_posix_info *info,
> struct cifs_sb_info *cifs_sb)
> {
> + unsigned int sbflags = cifs_sb_flags(cifs_sb);
> struct smb2_posix_info_parsed parsed;
>
> posix_info_parse(info, NULL, &parsed);
> @@ -281,8 +282,12 @@ cifs_posix_to_fattr(struct cifs_fattr *fattr, struct smb2_posix_info *info,
> le32_to_cpu(info->ReparseTag),
> le32_to_cpu(info->Mode));
>
> - sid_to_id(cifs_sb, &parsed.owner, fattr, SIDOWNER);
> - sid_to_id(cifs_sb, &parsed.group, fattr, SIDGROUP);
> + fattr->cf_uid = cifs_sb->ctx->linux_uid;
> + fattr->cf_gid = cifs_sb->ctx->linux_gid;
> + if (!(sbflags & CIFS_MOUNT_OVERR_UID))
> + sid_to_id(cifs_sb, &parsed.owner, fattr, SIDOWNER);
> + if (!(sbflags & CIFS_MOUNT_OVERR_GID))
> + sid_to_id(cifs_sb, &parsed.group, fattr, SIDGROUP);
> }
>
> static void __dir_info_to_fattr(struct cifs_fattr *fattr, const void *info)
> --
> 2.53.0
>
>
Does not apply :(
prev parent reply other threads:[~2026-09-17 10:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 16:42 FAILED: patch "[PATCH] smb: client: honor forceuid/forcegid when mapping SIDs to" failed to apply to 6.18-stable tree gregkh
2026-09-17 4:23 ` [PATCH 6.18.y 1/2] smb: client: use atomic_t for mnt_cifs_flags Sasha Levin
2026-09-17 4:23 ` [PATCH 6.18.y 2/2] smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid Sasha Levin
2026-09-17 10:11 ` Greg KH [this message]
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