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fuse: verify {g,u}id mount options correctly

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commit 525bd65aa7 upstream.

As was done in
0200679fc7 ("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: c30da2e981 ("fuse: convert to use the new mount API")
Cc: stable@vger.kernel.org # 5.4+
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Link: https://lore.kernel.org/r/8f07d45d-c806-484d-a2e3-7a2199df1cd2@redhat.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Sandeen 2024-07-02 17:22:41 -05:00 committed by Greg Kroah-Hartman
parent 054dc05f57
commit 794964ac11
1 changed files with 20 additions and 4 deletions
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24
fs/fuse/inode.c
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@ -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;