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| author | Al Viro <viro@zeniv.linux.org.uk> | 2013-02-22 22:45:42 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2013-02-22 23:31:05 -0500 |
| commit | 9b40bc90abd126bcc5da5658059b8e72e285e559 (patch) | |
| tree | b360cf7d9cf1f7e29f5f6b9c0193fbd1a75334a6 /fs/namespace.c | |
| parent | 3a142ed962958d3063f648738a3384ab90017100 (diff) | |
| download | lwn-9b40bc90abd126bcc5da5658059b8e72e285e559.tar.gz lwn-9b40bc90abd126bcc5da5658059b8e72e285e559.zip | |
get rid of unprotected dereferencing of mnt->mnt_ns
It's safe only under namespace_sem or vfsmount_lock; all places
in fs/namespace.c that want mnt->mnt_ns->user_ns actually want to use
current->nsproxy->mnt_ns->user_ns (note the calls of check_mnt() in
there).
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 29 |
1 files changed, 17 insertions, 12 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 55605c552787..edac42c6eff2 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1237,6 +1237,14 @@ static int do_umount(struct mount *mnt, int flags) return retval; } +/* + * Is the caller allowed to modify his namespace? + */ +static inline bool may_mount(void) +{ + return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); +} + /* * Now umount can handle mount points as well as block devices. * This is important for filesystems which use unnamed block devices. @@ -1255,6 +1263,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) return -EINVAL; + if (!may_mount()) + return -EPERM; + if (!(flags & UMOUNT_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; @@ -1268,10 +1279,6 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) if (!check_mnt(mnt)) goto dput_and_out; - retval = -EPERM; - if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) - goto dput_and_out; - retval = do_umount(mnt, flags); dput_and_out: /* we mustn't call path_put() as that would clear mnt_expiry_mark */ @@ -1295,7 +1302,7 @@ SYSCALL_DEFINE1(oldumount, char __user *, name) static int mount_is_safe(struct path *path) { - if (ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (may_mount()) return 0; return -EPERM; #ifdef notyet @@ -1633,7 +1640,7 @@ static int do_change_type(struct path *path, int flag) int type; int err = 0; - if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; if (path->dentry != path->mnt->mnt_root) @@ -1797,7 +1804,7 @@ static int do_move_mount(struct path *path, const char *old_name) struct mount *p; struct mount *old; int err = 0; - if (!ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; if (!old_name || !*old_name) return -EINVAL; @@ -1933,16 +1940,14 @@ static int do_new_mount(struct path *path, const char *fstype, int flags, int mnt_flags, const char *name, void *data) { struct file_system_type *type; - struct user_namespace *user_ns; + struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; struct vfsmount *mnt; int err; if (!fstype) return -EINVAL; - /* we need capabilities... */ - user_ns = real_mount(path->mnt)->mnt_ns->user_ns; - if (!ns_capable(user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; type = get_fs_type(fstype); @@ -2567,7 +2572,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, struct mount *new_mnt, *root_mnt; int error; - if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; error = user_path_dir(new_root, &new); |