Merge tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull /proc/sys dcache lookup fix from Al Viro:
"Fix for the breakage spotted by Neil in the interplay between
/proc/sys ->d_compare() weirdness and parallel lookups"
* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix proc_sys_compare() handling of in-lookup dentries
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index a3eb3b7..3604b61 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -42,7 +42,7 @@ static void proc_evict_inode(struct inode *inode)
head = ei->sysctl;
if (head) {
- RCU_INIT_POINTER(ei->sysctl, NULL);
+ WRITE_ONCE(ei->sysctl, NULL);
proc_sys_evict_inode(inode, head);
}
}
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index cc9d74a..08b7815 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -918,17 +918,21 @@ static int proc_sys_compare(const struct dentry *dentry,
struct ctl_table_header *head;
struct inode *inode;
- /* Although proc doesn't have negative dentries, rcu-walk means
- * that inode here can be NULL */
- /* AV: can it, indeed? */
- inode = d_inode_rcu(dentry);
- if (!inode)
- return 1;
if (name->len != len)
return 1;
if (memcmp(name->name, str, len))
return 1;
- head = rcu_dereference(PROC_I(inode)->sysctl);
+
+ // false positive is fine here - we'll recheck anyway
+ if (d_in_lookup(dentry))
+ return 0;
+
+ inode = d_inode_rcu(dentry);
+ // we just might have run into dentry in the middle of __dentry_kill()
+ if (!inode)
+ return 1;
+
+ head = READ_ONCE(PROC_I(inode)->sysctl);
return !head || !sysctl_is_seen(head);
}
