[PATCH] udf: KASAN: slab-out-of-bounds in udf_readdir

[Vladislav Efanov]

The KASAN report is:
[ 1922.586560] BUG: KASAN: slab-out-of-bounds in udf_readdir+0xe00/0x19e0
[ 1922.586922] Write of size 89 at addr ffff888000cd9ea6 by task rm/18493

udf_readdir() tries to write file name out of allocated memory
buffer bounds. The UDF_NAME_LEN_CS0 (255) is used as max length
for file name in udf_put_filename(). But UDF_NAME_LEN (254) is
used as the size for buffer allocation in udf_readdir(). As the
result out-of-bounds write happened.

Found by Linux Verification Center (linuxtesting.org) with xfstests

Fixes: 066b9cded00b ("udf: Use separate buffer for copying split names")
Signed-off-by: Vladislav Efanov <VEfanov@xxxxxxxxx>
---
 fs/udf/dir.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/dir.c b/fs/udf/dir.c
index be640f4b2f2c..b95607c42ad4 100644
--- a/fs/udf/dir.c
+++ b/fs/udf/dir.c
@@ -169,7 +169,7 @@ static int udf_readdir(struct file *file, struct dir_context *ctx)
 				nameptr = (char *)(fibh.ebh->b_data + poffset - lfi);
 			} else {
 				if (!copy_name) {
-					copy_name = kmalloc(UDF_NAME_LEN,
+					copy_name = kmalloc(UDF_NAME_LEN_CS0,
 							    GFP_NOFS);
 					if (!copy_name) {
 						ret = -ENOMEM;
-- 
2.34.1