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 <viro@xxxxxxxxxxxxxxxxxx> > 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@xxxxxxxxxxxxxxxxxxxxxxxxx > 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);
