@@ -755,6 +755,8 @@ static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param)
struct fs_parse_result result;
struct fuse_fs_context *ctx = fsc->fs_private;
int opt;
+ kuid_t kuid;
+ kgid_t kgid;
if (fsc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
/*
@@ -799,16 +801,30 @@ static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param)
break;
case OPT_USER_ID:
- ctx->user_id = make_kuid(fsc->user_ns, result.uint_32);
- if (!uid_valid(ctx->user_id))
+ kuid = make_kuid(fsc->user_ns, result.uint_32);
+ if (!uid_valid(kuid))
return invalfc(fsc, "Invalid user_id");
+ /*
+ * The requested uid must be representable in the
+ * filesystem's idmapping.
+ */
+ if (!kuid_has_mapping(fsc->user_ns, kuid))
+ return invalfc(fsc, "Invalid user_id");
+ ctx->user_id = kuid;
ctx->user_id_present = true;
break;
case OPT_GROUP_ID:
- ctx->group_id = make_kgid(fsc->user_ns, result.uint_32);
- if (!gid_valid(ctx->group_id))
+ kgid = make_kgid(fsc->user_ns, result.uint_32);;
+ if (!gid_valid(kgid))
+ return invalfc(fsc, "Invalid group_id");
+ /*
+ * The requested gid must be representable in the
+ * filesystem's idmapping.
+ */
+ if (!kgid_has_mapping(fsc->user_ns, kgid))
return invalfc(fsc, "Invalid group_id");
+ ctx->group_id = kgid;
ctx->group_id_present = true;
break;
As was done in 0200679fc795 ("tmpfs: verify {g,u}id mount options correctly") we need to validate that the requested uid and/or gid is representable in the filesystem's idmapping. Cribbing from the above commit log, The contract for {g,u}id mount options and {g,u}id values in general set from userspace has always been that they are translated according to the caller's idmapping. In so far, fuse has been doing the correct thing. But since fuse is mountable in unprivileged contexts it is also necessary to verify that the resulting {k,g}uid is representable in the namespace of the superblock. Fixes: c30da2e981a7 ("fuse: convert to use the new mount API") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Eric Sandeen <sandeen@redhat.com> --- p.s. sorry for the delay getting this posted fs/fuse/inode.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)