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@xxxxxxxxxxxxxx/ [1] Link: https://lore.kernel.org/all/CAJfpegtHQsEUuFq1k4ZbTD3E1h-GsrN3PWyv7X8cg6sfU_W2Yw@xxxxxxxxxxxxxx/ [2] Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: Seth Forshee <sforshee@xxxxxxxxxx> Cc: Miklos Szeredi <miklos@xxxxxxxxxx> Cc: Amir Goldstein <amir73il@xxxxxxxxx> Cc: Bernd Schubert <bschubert@xxxxxxx> Cc: <linux-fsdevel@xxxxxxxxxxxxxxx> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> --- v4: - this commit added --- fs/fuse/dev.c | 50 +++++++++++++++++++++++++++++---------- fs/fuse/inode.c | 1 + include/uapi/linux/fuse.h | 2 ++ 3 files changed, 41 insertions(+), 12 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 7146038b2fe7..d3f3c3557c04 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -103,7 +103,9 @@ 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; @@ -135,19 +137,37 @@ 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: @@ -466,8 +486,14 @@ 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); } @@ -499,7 +525,7 @@ 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); } @@ -560,7 +586,7 @@ 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); } @@ -583,7 +609,7 @@ static int fuse_simple_notify_reply(struct fuse_mount *fm, struct fuse_iqueue *fiq = &fm->fc->iq; int err = 0; - req = fuse_get_req(fm, false); + req = fuse_get_req(NULL, fm, false); if (IS_ERR(req)) return PTR_ERR(req); diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index d8ab4e93916f..115538f6f283 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1567,6 +1567,7 @@ 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); diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index d08b99d60f6f..2ccf38181df2 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -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; -- 2.34.1
