From 5cf79899db86bf963e12c98572e44fc34eb8499d Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Tue, 2 Jul 2024 17:22:41 -0500 Subject: [PATCH] fuse: verify {g,u}id mount options correctly [ Upstream commit 525bd65aa759ec320af1dc06e114ed69733e9e23 ] 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 Link: https://lore.kernel.org/r/8f07d45d-c806-484d-a2e3-7a2199df1cd2@redhat.com Reviewed-by: Christian Brauner Reviewed-by: Josef Bacik Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/fuse/inode.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 0a122a09e..12432770f 100755 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -541,6 +541,8 @@ 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) { /* @@ -585,16 +587,30 @@ 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;