Hi Amir, Thanks so much for this idea. On Fri, Sep 28, 2018 at 08:39:15PM +0300, Amir Goldstein wrote: > On Fri, Sep 28, 2018 at 5:55 PM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > > > On Fri, Sep 28, 2018 at 4:45 PM, syzbot > > <syzbot+376cea2b0ef340db3dd4@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > Hello, > > > > > > syzbot found the following crash on: > > > > > > HEAD commit: c127e59bee3e Merge tag 'for_v4.19-rc6' of git://git.kernel.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=13b2f32a400000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=dfb440e26f0a6f6f > > > dashboard link: https://syzkaller.appspot.com/bug?extid=376cea2b0ef340db3dd4 > > > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > > > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+376cea2b0ef340db3dd4@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > I guess this is overlayfs rather than printk. +overlayfs maintainers > > In future syzbot will avoid attributing crashes to printk, because I > > think it's not the first time crashes are mis-attributed to printk: > > https://github.com/google/syzkaller/commit/41e4b32952f4590341ae872db0abf819b4004713 > > > > > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000140 > > > RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000 > > > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0e714a76d4 > > > R13: 00000000004c32cb R14: 00000000004d4ef0 R15: 0000000000000004 > > > ================================================================== > > > BUG: KASAN: slab-out-of-bounds in string+0x298/0x2d0 lib/vsprintf.c:604 > > > Read of size 1 at addr ffff8801c36c66ba by task syz-executor2/27811 > > > > > > CPU: 0 PID: 27811 Comm: syz-executor2 Not tainted 4.19.0-rc5+ #36 > > > 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+0x1c4/0x2b4 lib/dump_stack.c:113 > > > print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 > > > kasan_report_error mm/kasan/report.c:354 [inline] > > > kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 > > > __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 > > > string+0x298/0x2d0 lib/vsprintf.c:604 > > > vsnprintf+0x48e/0x1b60 lib/vsprintf.c:2293 > > > vscnprintf+0x2d/0x80 lib/vsprintf.c:2396 > > > vprintk_store+0x43/0x510 kernel/printk/printk.c:1847 > > > vprintk_emit+0x1c1/0x930 kernel/printk/printk.c:1905 > > > vprintk_default+0x28/0x30 kernel/printk/printk.c:1963 > > > vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 > > > printk+0xa7/0xcf kernel/printk/printk.c:1996 > > > ovl_lookup_index.cold.15+0xe8/0x1f8 fs/overlayfs/namei.c:689 > > Doh! > I used %*s instead of %.s > Look how common this mistake is! and I only checked under fs/ > > [CC: Dan Carpenter and other fs maintainers] > Idea for static code analyzers: > A variable named *len* is probably not what someone wants to describe > the width of %*s field and in most cases I found were %*s is used correctly > the string value is a compiler constant (often ""). > > Thanks, > Amir. > > --- > diff --git a/fs/coda/dir.c b/fs/coda/dir.c > index 00876ddadb43..23ee5de8b4be 100644 > --- a/fs/coda/dir.c > +++ b/fs/coda/dir.c > @@ -47,7 +47,7 @@ static struct dentry *coda_lookup(struct inode *dir, > struct dentry *entry, unsig > int type = 0; > > if (length > CODA_MAXNAMLEN) { > - pr_err("name too long: lookup, %s (%*s)\n", > + pr_err("name too long: lookup, %s (%.*s)\n", This isn't the right fix because "length" is invalid. > coda_i2s(dir), (int)length, name); > return ERR_PTR(-ENAMETOOLONG); > } > diff --git a/fs/lockd/host.c b/fs/lockd/host.c > index d35cd6be0675..93fb7cf0b92b 100644 > --- a/fs/lockd/host.c > +++ b/fs/lockd/host.c > @@ -341,7 +341,7 @@ struct nlm_host *nlmsvc_lookup_host(const struct > svc_rqst *rqstp, > }; > struct lockd_net *ln = net_generic(net, lockd_net_id); > > - dprintk("lockd: %s(host='%*s', vers=%u, proto=%s)\n", __func__, > + dprintk("lockd: %s(host='%.*s', vers=%u, proto=%s)\n", __func__, > (int)hostname_len, hostname, rqstp->rq_vers, > (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp")); > Why wasn't this one applied? It looks correct to me. The rest seem to have been fixed already. I did find one other bug in wireless and I CC'd you on that. I'm going to do a little bit more testing on the check and then push it soon. Thanks again! regards, dan carpenter
