Commit df4c0e36 authored Feb 13, 2015 by Andrey Ryabinin Committed by Linus Torvalds Feb 13, 2015

fs: dcache: manually unpoison dname after allocation to shut up kasan's reports



We need to manually unpoison rounded up allocation size for dname to avoid
kasan's reports in dentry_string_cmp().  When CONFIG_DCACHE_WORD_ACCESS=y
dentry_string_cmp may access few bytes beyound requested in kmalloc()
size.

dentry_string_cmp() relates on that fact that dentry allocated using
kmalloc and kmalloc internally round up allocation size.  So this is not a
bug, but this makes kasan to complain about such accesses.  To avoid such
reports we mark rounded up allocation size in shadow as accessible.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Serebryany <kcc@google.com>
Cc: Dmitry Chernenkov <dmitryc@google.com>
Signed-off-by: Andrey Konovalov <adech.fo@gmail.com>
Cc: Yuri Gribov <tetra2005@gmail.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0316bec2

fs/dcache.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -38,6 +38,8 @@
		#include <linux/prefetch.h>
		#include <linux/ratelimit.h>
		#include <linux/list_lru.h>
		#include <linux/kasan.h>

		#include "internal.h"
		#include "mount.h"

		@@ -1429,6 +1431,9 @@ struct dentry __d_alloc(struct super_block sb, const struct qstr *name)
		}
		atomic_set(&p->u.count, 1);
		dname = p->name;
		if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS))
		kasan_unpoison_shadow(dname,
		round_up(name->len + 1, sizeof(unsigned long)));
		} else {
		dname = dentry->d_iname;
		}

Admin message