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smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid

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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
This commit is contained in:
Paulo Alcantara 2026-09-06 14:40:04 -03:00
parent cf4d358966
commit 18a72975e9
3 changed files with 32 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
fs/smb/client/cifsacl.c
View File

@ -1346,6 +1346,7 @@ 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;
@ -1364,17 +1365,21 @@ 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);
@ -1383,11 +1388,13 @@ 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) {

9
fs/smb/client/inode.c
View File

@ -851,6 +851,7 @@ 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));
@ -895,8 +896,12 @@ 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);

9
fs/smb/client/readdir.c
View File

@ -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)