On 10/13/21 19:51, syzbot wrote:
Hello,
syzbot found the following issue on:
HEAD commit: 717478d89fe2 Merge tag 'riscv-for-linus-5.15-rc5' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12489abf300000
kernel config: https://syzkaller.appspot.com/x/.config?x=32e6048063923b7b
dashboard link: https://syzkaller.appspot.com/bug?extid=2c56b725ec547fa9cb29
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=167b9e4f300000
The issue was bisected to:
commit 284562e1f34874e267d4f499362c3816f8f6bc3f
Author: Gurchetan Singh <gurchetansingh@xxxxxxxxxxxx>
Date: Tue Dec 3 01:36:27 2019 +0000
udmabuf: implement begin_cpu_access/end_cpu_access hooks
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12d68447300000
final oops: https://syzkaller.appspot.com/x/report.txt?x=11d68447300000
console output: https://syzkaller.appspot.com/x/log.txt?x=16d68447300000
zero ubuf->pagecount will cause kmalloc_array() to return ZERO_PTR, that
is unsafe to deref
#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
With regards,
Pavel Skripkin
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index c57a609db75b..e7330684d3b8 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -190,6 +190,10 @@ static long udmabuf_create(struct miscdevice *device,
if (ubuf->pagecount > pglimit)
goto err;
}
+
+ if (!ubuf->pagecount)
+ goto err;
+
ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
GFP_KERNEL);
if (!ubuf->pages) {
