From: Andrey Ryabinin a.ryabinin@samsung.com
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 (cherry picked from commit df4c0e36f1b1782b0611a77c52cc240e5c4752dd) Signed-off-by: Alex Shi alex.shi@linaro.org --- fs/dcache.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/fs/dcache.c b/fs/dcache.c index d25f8fd..da349a1 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -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"
@@ -1433,6 +1435,9 @@ 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; }