Messages in this thread | | | Date | Wed, 23 Feb 2022 09:38:20 -0500 | From | "" <> | Subject | Re: [syzbot] KASAN: use-after-free Read in dev_uevent |
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On Wed, Feb 23, 2022 at 12:29:03PM +0100, gregkh@linuxfoundation.org wrote: > On Wed, Feb 23, 2022 at 11:17:07AM +0000, Zhang, Qiang1 wrote: > > > > syzbot has found a reproducer for the following issue on: > > > > HEAD commit: 4f12b742eb2b Merge tag 'nfs-for-5.17-3' of git://git.linux.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=110a6df2700000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=f6a069ed94a1ed1d > > dashboard link: https://syzkaller.appspot.com/bug?extid=348b571beb5eeb70a582 > > 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=12377296700000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+348b571beb5eeb70a582@syzkaller.appspotmail.com > > > > ================================================================== > > BUG: KASAN: use-after-free in dev_uevent+0x712/0x780 drivers/base/core.c:2320 Read of size 8 at addr ffff88802b934098 by task udevd/3689 > > > > CPU: 2 PID: 3689 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: > > <TASK> > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > > print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255 __kasan_report mm/kasan/report.c:442 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 > > dev_uevent+0x712/0x780 drivers/base/core.c:2320 > > uevent_show+0x1b8/0x380 drivers/base/core.c:2391 > > dev_attr_show+0x4b/0x90 drivers/base/core.c:2094 > > sysfs_kf_seq_show+0x219/0x3d0 fs/sysfs/file.c:59 > > seq_read_iter+0x4f5/0x1280 fs/seq_file.c:230 > > kernfs_fop_read_iter+0x514/0x6f0 fs/kernfs/file.c:241 call_read_iter include/linux/fs.h:2068 [inline] > > new_sync_read+0x429/0x6e0 fs/read_write.c:400 > > vfs_read+0x35c/0x600 fs/read_write.c:481 > > ksys_read+0x12d/0x250 fs/read_write.c:619 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae > > RIP: 0033:0x7f964cc558fe > > Code: c0 e9 e6 fe ff ff 50 48 8d 3d 0e c7 09 00 e8 c9 cf 01 00 66 0f 1f 84 00 00 00 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 66 0f 1f 84 00 00 00 00 00 48 83 ec 28 > > RSP: 002b:00007ffc0133d258 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > > RAX: ffffffffffffffda RBX: 000056497b21a140 RCX: 00007f964cc558fe > > RDX: 0000000000001000 RSI: 000056497b218650 RDI: 0000000000000008 > > RBP: 00007f964cd22380 R08: 0000000000000008 R09: 00007f964cd25a60 > > R10: 0000000000000008 R11: 0000000000000246 R12: 000056497b21a140 > > R13: 0000000000000d68 R14: 00007f964cd21780 R15: 0000000000000d68 </TASK> > > > > Cc: Alan Stern > > Felipe Balbi > > > > Hello syzbot, Please try it: > > > > From 574d45ff924e2d2f9b9f5cc3e846f8004498a811 Mon Sep 17 00:00:00 2001 > > From: Zqiang <qiang1.zhang@intel.com> > > Date: Wed, 23 Feb 2022 18:18:22 +0800 > > Subject: [PATCH] driver core: Fix use-after-free in dev_uevent() > > > > In dev_uevent(), if the "dev->driver" is valid, the "dev->driver->name" > > be accessed, there may be a window period between these two operations. > > There should not be any such window period. The bus locks should > prevent this, unless some driver is doing odd things with the pointers > that it should not be doing.
Which bus locks are you referring to? I'm not aware of any locks that synchronize dev_uevent() with anything (in particular, with driver unbinding).
And as far as I know, usb_gadget_remove_driver() doesn't play any odd tricks with pointers.
> > in this window period if the "dev->driver" is set to null > > (in usb_gadget_unregister_driver function), when the "dev->driver->name" > > is accessed again, invalid address will be accessed. fix it by checking > > "dev->driver" again. > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > --- > > drivers/base/core.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > index 3d6430eb0c6a..a45b927ee76e 100644 > > --- a/drivers/base/core.c > > +++ b/drivers/base/core.c > > @@ -2317,7 +2317,7 @@ static int dev_uevent(struct kobject *kobj, struct kobj_uevent_env *env) > > add_uevent_var(env, "DEVTYPE=%s", dev->type->name); > > > > if (dev->driver) > > - add_uevent_var(env, "DRIVER=%s", dev->driver->name); > > + add_uevent_var(env, "DRIVER=%s", dev_driver_string(dev)); > > What's to prevent the "window" from happening in the middle of the > dev_driver_string() call?
Nothing prevents it. But if you read the code for dev_driver_string(), you will see that it doesn't matter if dev->driver gets set to NULL while the routine is running.
(Of course, there is still the possibility that the driver structure itself might get deallocated while dev_driver_string() is running. This whole area could perhaps use a little careful thought. Driver unbinding might be a good application for SRCU.)
Alan Stern
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