Re: [PATCH 3.10 14/46] d_walk() might skip too much

[Jari Ruusu]

When Al Viro's VFS deadlock fix "deal with deadlock in d_walk()" was
backported to 3.10.y 3.4.y and 3.2.y stable kernel brances, the deadlock fix
was copied to 3 different places. Later, a bug in that code was discovered.
Al Viro's fix involved fixing only one part of code in mainline kernel. That
fix is called "d_walk() might skip too much".

3.10.y 3.4.y and 3.2.y stable kernel brances need that later fix copied to 3
different places. Greg Kroah-Hartman included Al Viro's "d_walk() might skip
too much" fix only once in 3.10.80 kernel, leaving 2 more places without a
fix.

The patch below was not written by me. I only applied Al Viro's "d_walk()
might skip too much" fix 2 more times to 3.10.80 kernel, and cheched that
the fixes went to correct places. With this patch applied, all 3 places that
I am aware of 3.10.y stable branch are now fixed.

Signed-off-by: Jari Ruusu <jariruusu@xxxxxxxxxxxxxxxxxxxxx>

--- linux-3.10.80/fs/dcache.c.OLD	2015-06-11 19:22:31.000000000 +0300
+++ linux-3.10.80/fs/dcache.c	2015-06-11 19:32:59.000000000 +0300
@@ -1053,13 +1053,13 @@
 		/* might go back up the wrong parent if we have had a rename. */
 		if (!locked && read_seqretry(&rename_lock, seq))
 			goto rename_retry;
-		next = child->d_child.next;
-		while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {
+		/* go into the first sibling still alive */
+		do {
+			next = child->d_child.next;
 			if (next == &this_parent->d_subdirs)
 				goto ascend;
 			child = list_entry(next, struct dentry, d_child);
-			next = next->next;
-		}
+		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
 		rcu_read_unlock();
 		goto resume;
 	}
@@ -2977,13 +2977,13 @@
 		/* might go back up the wrong parent if we have had a rename. */
 		if (!locked && read_seqretry(&rename_lock, seq))
 			goto rename_retry;
-		next = child->d_child.next;
-		while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {
+		/* go into the first sibling still alive */
+		do {
+			next = child->d_child.next;
 			if (next == &this_parent->d_subdirs)
 				goto ascend;
 			child = list_entry(next, struct dentry, d_child);
-			next = next->next;
-		}
+		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
 		rcu_read_unlock();
 		goto resume;
 	}

-- 
Jari Ruusu  4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD  ACDF F073 3C80 8132 F189
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/