diff options
Diffstat (limited to 'sys/kern/vfs_cache.c')
| -rw-r--r-- | sys/kern/vfs_cache.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index 0610b685267c..5440ee3e1ac1 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -2811,6 +2811,7 @@ vn_fullpath_hardlink(struct thread *td, struct nameidata *ndp, char **retbuf, size_t addend; int error; bool slash_prefixed; + enum vtype type; if (*buflen < 2) return (EINVAL); @@ -2824,7 +2825,31 @@ vn_fullpath_hardlink(struct thread *td, struct nameidata *ndp, char **retbuf, addend = 0; vp = ndp->ni_vp; - if (vp->v_type != VDIR) { + /* + * Check for VBAD to work around the vp_crossmp bug in lookup(). + * + * For example consider tmpfs on /tmp and realpath /tmp. ni_vp will be + * set to mount point's root vnode while ni_dvp will be vp_crossmp. + * If the type is VDIR (like in this very case) we can skip looking + * at ni_dvp in the first place. However, since vnodes get passed here + * unlocked the target may transition to doomed state (type == VBAD) + * before we get to evaluate the condition. If this happens, we will + * populate part of the buffer and descend to vn_fullpath_dir with + * vp == vp_crossmp. Prevent the problem by checking for VBAD. + * + * This should be atomic_load(&vp->v_type) but it is ilegal to take + * an address of a bit field, even if said field is sized to char. + * Work around the problem by reading the value into a full-sized enum + * and then re-reading it with atomic_load which will still prevent + * the compiler from re-reading down the road. + */ + type = vp->v_type; + type = atomic_load_int(&type); + if (type == VBAD) { + error = ENOENT; + goto out_bad; + } + if (type != VDIR) { cnp = &ndp->ni_cnd; addend = cnp->cn_namelen + 2; if (*buflen < addend) { |