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fuse: add basic infrastructure to support idmappings

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Add some preparational changes in fuse_get_req/fuse_force_creds
to handle idmappings.

Miklos suggested [1], [2] to change the meaning of in.h.uid/in.h.gid
fields when daemon declares support for idmapped mounts. In a new semantic,
we fill uid/gid values in fuse header with a id-mapped caller uid/gid (for
requests which create new inodes), for all the rest cases we just send -1
to userspace.

No functional changes intended.

Link: https://lore.kernel.org/all/CAJfpegsVY97_5mHSc06mSw79FehFWtoXT=hhTUK_E-Yhr7OAuQ@mail.gmail.com/ [1]
Link: https://lore.kernel.org/all/CAJfpegtHQsEUuFq1k4ZbTD3E1h-GsrN3PWyv7X8cg6sfU_W2Yw@mail.gmail.com/ [2]
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Alexander Mikhalitsyn 2024-09-03 17:16:13 +02:00 committed by Miklos Szeredi
parent 2097154a10
commit aa16880d9f
3 changed files with 41 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
fs/fuse/dev.c
View File

@ -108,7 +108,9 @@ static void fuse_drop_waiting(struct fuse_conn *fc)
static void fuse_put_request(struct fuse_req *req);
static struct fuse_req *fuse_get_req(struct fuse_mount *fm, bool for_background)
static struct fuse_req *fuse_get_req(struct mnt_idmap *idmap,
struct fuse_mount *fm,
bool for_background)
{
struct fuse_conn *fc = fm->fc;
struct fuse_req *req;
@ -140,19 +142,37 @@ static struct fuse_req *fuse_get_req(struct fuse_mount *fm, bool for_background)
goto out;
}
req->in.h.uid = from_kuid(fc->user_ns, current_fsuid());
req->in.h.gid = from_kgid(fc->user_ns, current_fsgid());
req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
__set_bit(FR_WAITING, &req->flags);
if (for_background)
__set_bit(FR_BACKGROUND, &req->flags);
if (unlikely(req->in.h.uid == ((uid_t)-1) ||
req->in.h.gid == ((gid_t)-1))) {
fuse_put_request(req);
return ERR_PTR(-EOVERFLOW);
if ((fm->sb->s_iflags & SB_I_NOIDMAP) || idmap) {
kuid_t idmapped_fsuid;
kgid_t idmapped_fsgid;
/*
* Note, that when
* (fm->sb->s_iflags & SB_I_NOIDMAP) is true, then
* (idmap == &nop_mnt_idmap) is always true and therefore,
* mapped_fsuid(idmap, fc->user_ns) == current_fsuid().
*/
idmapped_fsuid = idmap ? mapped_fsuid(idmap, fc->user_ns) : current_fsuid();
idmapped_fsgid = idmap ? mapped_fsgid(idmap, fc->user_ns) : current_fsgid();
req->in.h.uid = from_kuid(fc->user_ns, idmapped_fsuid);
req->in.h.gid = from_kgid(fc->user_ns, idmapped_fsgid);
if (unlikely(req->in.h.uid == ((uid_t)-1) ||
req->in.h.gid == ((gid_t)-1))) {
fuse_put_request(req);
return ERR_PTR(-EOVERFLOW);
}
} else {
req->in.h.uid = FUSE_INVALID_UIDGID;
req->in.h.gid = FUSE_INVALID_UIDGID;
}
return req;
out:
@ -497,8 +517,14 @@ static void fuse_force_creds(struct fuse_req *req)
{
struct fuse_conn *fc = req->fm->fc;
req->in.h.uid = from_kuid_munged(fc->user_ns, current_fsuid());
req->in.h.gid = from_kgid_munged(fc->user_ns, current_fsgid());
if (req->fm->sb->s_iflags & SB_I_NOIDMAP) {
req->in.h.uid = from_kuid_munged(fc->user_ns, current_fsuid());
req->in.h.gid = from_kgid_munged(fc->user_ns, current_fsgid());
} else {
req->in.h.uid = FUSE_INVALID_UIDGID;
req->in.h.gid = FUSE_INVALID_UIDGID;
}
req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
}
@ -530,7 +556,7 @@ ssize_t fuse_simple_request(struct fuse_mount *fm, struct fuse_args *args)
__set_bit(FR_FORCE, &req->flags);
} else {
WARN_ON(args->nocreds);
req = fuse_get_req(fm, false);
req = fuse_get_req(NULL, fm, false);
if (IS_ERR(req))
return PTR_ERR(req);
}
@ -591,7 +617,7 @@ int fuse_simple_background(struct fuse_mount *fm, struct fuse_args *args,
__set_bit(FR_BACKGROUND, &req->flags);
} else {
WARN_ON(args->nocreds);
req = fuse_get_req(fm, true);
req = fuse_get_req(NULL, fm, true);
if (IS_ERR(req))
return PTR_ERR(req);
}
@ -613,7 +639,7 @@ static int fuse_simple_notify_reply(struct fuse_mount *fm,
struct fuse_req *req;
struct fuse_iqueue *fiq = &fm->fc->iq;
req = fuse_get_req(fm, false);
req = fuse_get_req(NULL, fm, false);
if (IS_ERR(req))
return PTR_ERR(req);

1
fs/fuse/inode.c
View File

@ -1572,6 +1572,7 @@ static void fuse_sb_defaults(struct super_block *sb)
sb->s_time_gran = 1;
sb->s_export_op = &fuse_export_operations;
sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
sb->s_iflags |= SB_I_NOIDMAP;
if (sb->s_user_ns != &init_user_ns)
sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);

2
include/uapi/linux/fuse.h
View File

@ -984,6 +984,8 @@ struct fuse_fallocate_in {
*/
#define FUSE_UNIQUE_RESEND (1ULL << 63)
#define FUSE_INVALID_UIDGID ((uint32_t)(-1))
struct fuse_in_header {
uint32_t len;
uint32_t opcode;