From: Viacheslav Dubeyko Date: Tue, 3 Feb 2026 22:54:46 +0000 (-0800) Subject: ceph: fix NULL pointer dereference in ceph_mds_auth_match() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7987cce375ac8ce98e170a77aa2399f2cf6eb99f;p=thirdparty%2Fkernel%2Flinux.git ceph: fix NULL pointer dereference in ceph_mds_auth_match() The CephFS kernel client has regression starting from 6.18-rc1. We have issue in ceph_mds_auth_match() if fs_name == NULL: const char fs_name = mdsc->fsc->mount_options->mds_namespace; ... if (auth->match.fs_name && strcmp(auth->match.fs_name, fs_name)) { / fsname mismatch, try next one */ return 0; } Patrick Donnelly suggested that: In summary, we should definitely start decoding `fs_name` from the MDSMap and do strict authorizations checks against it. Note that the `-o mds_namespace=foo` should only be used for selecting the file system to mount and nothing else. It's possible no mds_namespace is specified but the kernel will mount the only file system that exists which may have name "foo". This patch reworks ceph_mdsmap_decode() and namespace_equals() with the goal of supporting the suggested concept. Now struct ceph_mdsmap contains m_fs_name field that receives copy of extracted FS name by ceph_extract_encoded_string(). For the case of "old" CephFS file systems, it is used "cephfs" name. [ idryomov: replace redundant %*pE with %s in ceph_mdsmap_decode(), get rid of a series of strlen() calls in ceph_namespace_match(), drop changes to namespace_equals() body to avoid treating empty mds_namespace as equal, drop changes to ceph_mdsc_handle_fsmap() as namespace_equals() isn't an equivalent substitution there ] Cc: stable@vger.kernel.org Fixes: 22c73d52a6d0 ("ceph: fix multifs mds auth caps issue") Link: https://tracker.ceph.com/issues/73886 Signed-off-by: Viacheslav Dubeyko Reviewed-by: Patrick Donnelly Tested-by: Patrick Donnelly Signed-off-by: Ilya Dryomov --- diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 7e4eab824dae..c45bd19d4b1c 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -5671,7 +5671,7 @@ static int ceph_mds_auth_match(struct ceph_mds_client *mdsc, u32 caller_uid = from_kuid(&init_user_ns, cred->fsuid); u32 caller_gid = from_kgid(&init_user_ns, cred->fsgid); struct ceph_client *cl = mdsc->fsc->client; - const char *fs_name = mdsc->fsc->mount_options->mds_namespace; + const char *fs_name = mdsc->mdsmap->m_fs_name; const char *spath = mdsc->fsc->mount_options->server_path; bool gid_matched = false; u32 gid, tlen, len; @@ -5679,7 +5679,8 @@ static int ceph_mds_auth_match(struct ceph_mds_client *mdsc, doutc(cl, "fsname check fs_name=%s match.fs_name=%s\n", fs_name, auth->match.fs_name ? auth->match.fs_name : ""); - if (auth->match.fs_name && strcmp(auth->match.fs_name, fs_name)) { + + if (!ceph_namespace_match(auth->match.fs_name, fs_name)) { /* fsname mismatch, try next one */ return 0; } diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c index 2c7b151a7c95..b228e5ecfb92 100644 --- a/fs/ceph/mdsmap.c +++ b/fs/ceph/mdsmap.c @@ -353,22 +353,33 @@ struct ceph_mdsmap *ceph_mdsmap_decode(struct ceph_mds_client *mdsc, void **p, __decode_and_drop_type(p, end, u8, bad_ext); } if (mdsmap_ev >= 8) { - u32 fsname_len; + size_t fsname_len; + /* enabled */ ceph_decode_8_safe(p, end, m->m_enabled, bad_ext); + /* fs_name */ - ceph_decode_32_safe(p, end, fsname_len, bad_ext); + m->m_fs_name = ceph_extract_encoded_string(p, end, + &fsname_len, + GFP_NOFS); + if (IS_ERR(m->m_fs_name)) { + m->m_fs_name = NULL; + goto nomem; + } /* validate fsname against mds_namespace */ - if (!namespace_equals(mdsc->fsc->mount_options, *p, + if (!namespace_equals(mdsc->fsc->mount_options, m->m_fs_name, fsname_len)) { - pr_warn_client(cl, "fsname %*pE doesn't match mds_namespace %s\n", - (int)fsname_len, (char *)*p, + pr_warn_client(cl, "fsname %s doesn't match mds_namespace %s\n", + m->m_fs_name, mdsc->fsc->mount_options->mds_namespace); goto bad; } - /* skip fsname after validation */ - ceph_decode_skip_n(p, end, fsname_len, bad); + } else { + m->m_enabled = false; + m->m_fs_name = kstrdup(CEPH_OLD_FS_NAME, GFP_NOFS); + if (!m->m_fs_name) + goto nomem; } /* damaged */ if (mdsmap_ev >= 9) { @@ -430,6 +441,7 @@ void ceph_mdsmap_destroy(struct ceph_mdsmap *m) kfree(m->m_info); } kfree(m->m_data_pg_pools); + kfree(m->m_fs_name); kfree(m); } diff --git a/fs/ceph/mdsmap.h b/fs/ceph/mdsmap.h index 1f2171dd01bf..d48d07c3516d 100644 --- a/fs/ceph/mdsmap.h +++ b/fs/ceph/mdsmap.h @@ -45,6 +45,7 @@ struct ceph_mdsmap { bool m_enabled; bool m_damaged; int m_num_laggy; + char *m_fs_name; }; static inline struct ceph_entity_addr * diff --git a/fs/ceph/super.h b/fs/ceph/super.h index a1f781c46b41..29a980e22dc2 100644 --- a/fs/ceph/super.h +++ b/fs/ceph/super.h @@ -104,14 +104,26 @@ struct ceph_mount_options { struct fscrypt_dummy_policy dummy_enc_policy; }; +#define CEPH_NAMESPACE_WILDCARD "*" + +static inline bool ceph_namespace_match(const char *pattern, + const char *target) +{ + if (!pattern || !pattern[0] || + !strcmp(pattern, CEPH_NAMESPACE_WILDCARD)) + return true; + + return !strcmp(pattern, target); +} + /* * Check if the mds namespace in ceph_mount_options matches * the passed in namespace string. First time match (when * ->mds_namespace is NULL) is treated specially, since * ->mds_namespace needs to be initialized by the caller. */ -static inline int namespace_equals(struct ceph_mount_options *fsopt, - const char *namespace, size_t len) +static inline bool namespace_equals(struct ceph_mount_options *fsopt, + const char *namespace, size_t len) { return !(fsopt->mds_namespace && (strlen(fsopt->mds_namespace) != len || diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h index c7f2c63b3bc3..08e5dbe15ca4 100644 --- a/include/linux/ceph/ceph_fs.h +++ b/include/linux/ceph/ceph_fs.h @@ -31,6 +31,12 @@ #define CEPH_INO_CEPH 2 /* hidden .ceph dir */ #define CEPH_INO_GLOBAL_SNAPREALM 3 /* global dummy snaprealm */ +/* + * name for "old" CephFS file systems, + * see ceph.git e2b151d009640114b2565c901d6f41f6cd5ec652 + */ +#define CEPH_OLD_FS_NAME "cephfs" + /* arbitrary limit on max # of monitors (cluster of 3 is typical) */ #define CEPH_MAX_MON 31