Re: KASAN: slab-out-of-bounds Read in bpf_prog_create
From: Eric Biggers <ebiggers@kernel.org>
Date: 2019-09-28 03:15:19
Also in:
bpf, linux-fsdevel, lkml
Subsystem:
networking drivers, ppp protocol drivers and compressors, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Arnd and Al, On Tue, Sep 17, 2019 at 11:49:06AM -0700, syzbot wrote:
Hello, syzbot found the following crash on: HEAD commit: 2015a28f Add linux-next specific files for 20190915 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=11880d69600000 kernel config: https://syzkaller.appspot.com/x/.config?x=110691c2286b679a dashboard link: https://syzkaller.appspot.com/bug?extid=eb853b51b10f1befa0b7 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127c3481600000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1150a70d600000 The bug was bisected to: commit 2f4fa2db75e26995709043c8d3de4632ebed5c4b Author: Al Viro [off-list ref] Date: Thu Apr 18 03:48:01 2019 +0000 compat_ioctl: unify copy-in of ppp filters bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=145eee1d600000 final crash: https://syzkaller.appspot.com/x/report.txt?x=165eee1d600000 console output: https://syzkaller.appspot.com/x/log.txt?x=125eee1d600000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+eb853b51b10f1befa0b7@syzkaller.appspotmail.com Fixes: 2f4fa2db75e2 ("compat_ioctl: unify copy-in of ppp filters") ================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:404 [inline] BUG: KASAN: slab-out-of-bounds in bpf_prog_create+0xe9/0x250 net/core/filter.c:1351 Read of size 32768 at addr ffff88809cf74000 by task syz-executor183/8575 CPU: 0 PID: 8575 Comm: syz-executor183 Not tainted 5.3.0-rc8-next-20190915 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:634 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 memcpy+0x24/0x50 mm/kasan/common.c:122 memcpy include/linux/string.h:404 [inline] bpf_prog_create+0xe9/0x250 net/core/filter.c:1351 get_filter.isra.0+0x108/0x1a0 drivers/net/ppp/ppp_generic.c:572 ppp_get_filter drivers/net/ppp/ppp_generic.c:584 [inline] ppp_ioctl+0x129d/0x2590 drivers/net/ppp/ppp_generic.c:801
This is a correct bisection. This commit needs:
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 267fe2c58087..f55d7937d6c5 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c@@ -564,8 +564,9 @@ static struct bpf_prog *get_filter(struct sock_fprog *uprog) return NULL; /* uprog->len is unsigned short, so no overflow here */ - fprog.len = uprog->len * sizeof(struct sock_filter); - fprog.filter = memdup_user(uprog->filter, fprog.len); + fprog.len = uprog->len; + fprog.filter = memdup_user(uprog->filter, + uprog->len * sizeof(struct sock_filter)); if (IS_ERR(fprog.filter)) return ERR_CAST(fprog.filter);