[syzbot] KASAN: use-after-free Read in em28xx_close_extension

[syzbot] KASAN: use-after-free Read in em28xx_close_extension

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    3dbdb38e Merge branch 'for-5.14' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=158cf1e2300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a1fcf15a09815757
dashboard link: https://syzkaller.appspot.com/bug?extid=005037419ebdf14e1d87
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=169746b0300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=157e89c4300000

The issue was bisected to:

commit ac5688637144644f06ed1f3c6d4dd8bb7db96020
Author: Igor Matheus Andrade Torrente <igormtorrente@gmail.com>
Date:   Tue May 4 18:32:49 2021 +0000

    media: em28xx: Fix possible memory leak of em28xx struct

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1742cffc300000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=14c2cffc300000
console output: https://syzkaller.appspot.com/x/log.txt?x=10c2cffc300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+005037419ebdf14e1d87@syzkaller.appspotmail.com
Fixes: ac5688637144 ("media: em28xx: Fix possible memory leak of em28xx struct")

usb 1-1: bad CDC descriptors
usb 1-1: USB disconnect, device number 2
em28xx 1-1:64.138: Disconnecting em28xx
em28xx 1-1:64.138: Closing input extension
em28xx 1-1:64.138: Freeing device
==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0xcc/0xf0 lib/list_debug.c:42
Read of size 8 at addr ffff888021aa8258 by task kworker/1:2/3456

CPU: 1 PID: 3456 Comm: kworker/1:2 Not tainted 5.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
 print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
 __kasan_report mm/kasan/report.c:419 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
 __list_del_entry_valid+0xcc/0xf0 lib/list_debug.c:42
 __list_del_entry include/linux/list.h:132 [inline]
 list_del include/linux/list.h:146 [inline]
 em28xx_close_extension+0x10b/0x2a0 drivers/media/usb/em28xx/em28xx-core.c:1146
 em28xx_usb_disconnect.cold+0x14b/0x237 drivers/media/usb/em28xx/em28xx-cards.c:4140
 usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:458
 __device_release_driver+0x3bd/0x6f0 drivers/base/dd.c:1181
 device_release_driver_internal drivers/base/dd.c:1212 [inline]
 device_release_driver+0x26/0x40 drivers/base/dd.c:1235
 bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533
 device_del+0x502/0xd40 drivers/base/core.c:3512
 usb_disable_device+0x35b/0x7b0 drivers/usb/core/message.c:1413
 usb_disconnect.cold+0x27a/0x78e drivers/usb/core/hub.c:2221
 hub_port_connect drivers/usb/core/hub.c:5129 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5418 [inline]
 port_event drivers/usb/core/hub.c:5564 [inline]
 hub_event+0x1c9c/0x4330 drivers/usb/core/hub.c:5646
 process_one_work+0x98d/0x1630 kernel/workqueue.c:2276
 process_scheduled_works kernel/workqueue.c:2338 [inline]
 worker_thread+0x85c/0x11f0 kernel/workqueue.c:2424
 kthread+0x3e5/0x4d0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the page:
page:ffffea000086aa00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x21aa8
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000ac0d08 ffff8880b9d3b288 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), pid 3456, ts 70583523123, free_ts 71218691485
 prep_new_page mm/page_alloc.c:2445 [inline]
 get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4178
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5386
 alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
 kmalloc_order+0x34/0xf0 mm/slab_common.c:945
 kmalloc_order_trace+0x14/0x120 mm/slab_common.c:961
 kmalloc_large include/linux/slab.h:520 [inline]
 kmalloc include/linux/slab.h:584 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 em28xx_usb_probe+0x1f7/0xd00 drivers/media/usb/em28xx/em28xx-cards.c:3855
 usb_probe_interface+0x315/0x7f0 drivers/usb/core/driver.c:396
 really_probe+0x291/0xf60 drivers/base/dd.c:576
 driver_probe_device+0x298/0x410 drivers/base/dd.c:763
 __device_attach_driver+0x203/0x2c0 drivers/base/dd.c:870
 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431
 __device_attach+0x228/0x4a0 drivers/base/dd.c:938
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491
 device_add+0xbe0/0x2100 drivers/base/core.c:3324
 usb_set_configuration+0x113f/0x1910 drivers/usb/core/message.c:2164
 usb_generic_driver_probe+0xba/0x100 drivers/usb/core/generic.c:238
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1355 [inline]
 free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1406
 free_unref_page_prepare mm/page_alloc.c:3341 [inline]
 free_unref_page+0x19/0x690 mm/page_alloc.c:3420
 __refcount_sub_and_test include/linux/refcount.h:282 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 kref_put.constprop.0.isra.0+0x3d/0x7e include/linux/kref.h:64
 em28xx_ir_fini.cold+0x7c/0x120 drivers/media/usb/em28xx/em28xx-input.c:875
 em28xx_close_extension+0xc9/0x2a0 drivers/media/usb/em28xx/em28xx-core.c:1143
 em28xx_usb_disconnect.cold+0x14b/0x237 drivers/media/usb/em28xx/em28xx-cards.c:4140
 usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:458
 __device_release_driver+0x3bd/0x6f0 drivers/base/dd.c:1181
 device_release_driver_internal drivers/base/dd.c:1212 [inline]
 device_release_driver+0x26/0x40 drivers/base/dd.c:1235
 bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533
 device_del+0x502/0xd40 drivers/base/core.c:3512
 usb_disable_device+0x35b/0x7b0 drivers/usb/core/message.c:1413
 usb_disconnect.cold+0x27a/0x78e drivers/usb/core/hub.c:2221
 hub_port_connect drivers/usb/core/hub.c:5129 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5418 [inline]
 port_event drivers/usb/core/hub.c:5564 [inline]
 hub_event+0x1c9c/0x4330 drivers/usb/core/hub.c:5646
 process_one_work+0x98d/0x1630 kernel/workqueue.c:2276
 process_scheduled_works kernel/workqueue.c:2338 [inline]
 worker_thread+0x85c/0x11f0 kernel/workqueue.c:2424

Memory state around the buggy address:
 ffff888021aa8100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888021aa8180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888021aa8200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                    ^
 ffff888021aa8280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888021aa8300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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See https://goo.gl/tpsmEJ for more information about syzbot.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: [syzbot] KASAN: use-after-free Read in em28xx_close_extension

[Dan Carpenter]

On Tue, Jul 27, 2021 at 06:01:51PM +0800, Hillf Danton wrote:
> Along the probe path,
> 
> em28xx_usb_probe
>   dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>   retval = em28xx_init_dev(dev, udev, intf, nr);
>     em28xx_init_extension(dev);
>       em28xx_ir_init(struct em28xx *dev)
>         kref_get(&dev->ref);
> 
>   kref_init(&dev->ref);

Good detective work.

I've created a Smatch check to try find these.  It uses the fact that
Smatch creates a bunch of fake assignments to set all the struct members
of "dev" to zero.  Then it uses the modification hook to find the
kref_init().  Those are sort of new uses for those hooks so that's quite
fun.

I'll test it out overnight and see how it works.

drivers/media/usb/em28xx/em28xx-cards.c:4086 em28xx_usb_probe() warn: kref has already been modifed (see line 3979)

regards,
dan carpenter

#include "smatch.h"
#include "smatch_slist.h"
#include "smatch_extra.h"

static int my_id;

STATE(fresh);

static int get_line(struct sm_state *sm)
{
	struct sm_state *tmp;
	int line = 0;

	FOR_EACH_PTR(sm->possible, tmp) {
		if (tmp->state == &undefined &&
		    tmp->line > line)
			line = tmp->line;
	} END_FOR_EACH_PTR(tmp);

	if (!line)
		return sm->line;
	return line;
}

static void match_modify(struct sm_state *sm, struct expression *mod_expr)
{
	if (sm->state != &fresh &&
	    mod_expr &&
	    mod_expr->type == EXPR_CALL &&
	    sym_name_is("kref_init", mod_expr->fn))
		sm_warning("kref has already been modifed (see line %d)", get_line(sm));

	set_state(my_id, sm->name, sm->sym, &undefined);
}

static bool is_alloc(struct expression *expr)
{
	static struct expression *ignore, *alloc_expr;
	struct expression *right;

	if (!expr || expr->type != EXPR_ASSIGNMENT || expr->op != '=')
		return false;
	if (expr == ignore)
		return false;
	if (expr == alloc_expr)
		return true;
	right = strip_expr(expr->right);
	if (right->type == EXPR_CALL &&
	    (sym_name_is("kzalloc", right->fn) ||
	     sym_name_is("kmalloc", right->fn))) {
		alloc_expr = expr;
		return true;
	}
	ignore = expr;
	return false;
}

static void match_assign(struct expression *expr)
{
	char *name;

	if (!is_alloc(get_faked_expression()))
		return;
	name = expr_to_str(expr->left);
	if (name && strstr(name, "refcount.refs.counter"))
		set_state_expr(my_id, expr->left, &fresh);
	free_string(name);
}

void check_kref_init_too_late(int id)
{
	my_id = id;

	add_hook(&match_assign, ASSIGNMENT_HOOK_AFTER);
	add_modification_hook(my_id, &match_modify);
}

Re: [syzbot] KASAN: use-after-free Read in em28xx_close_extension

[Dongliang Mu]

On Tue, Jul 27, 2021 at 10:15 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> On Tue, Jul 27, 2021 at 06:01:51PM +0800, Hillf Danton wrote:
> > Along the probe path,
> >
> > em28xx_usb_probe
> >   dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> >   retval = em28xx_init_dev(dev, udev, intf, nr);
> >     em28xx_init_extension(dev);
> >       em28xx_ir_init(struct em28xx *dev)
> >         kref_get(&dev->ref);
> >
> >   kref_init(&dev->ref);
>

Hi Dan,

I have developed a patch [1] to fix this crash. Would you like to help
me double-check if it correctly fixes the underlying bug?

[1] [PATCH v2] [media] em28xx-input: fix refcount bug in
em28xx_usb_disconnect  https://lkml.org/lkml/2021/7/19/263

> Good detective work.
>
> I've created a Smatch check to try find these.  It uses the fact that
> Smatch creates a bunch of fake assignments to set all the struct members
> of "dev" to zero.  Then it uses the modification hook to find the
> kref_init().  Those are sort of new uses for those hooks so that's quite
> fun.
>
> I'll test it out overnight and see how it works.
>
> drivers/media/usb/em28xx/em28xx-cards.c:4086 em28xx_usb_probe() warn: kref has already been modifed (see line 3979)
>
> regards,
> dan carpenter
>
> #include "smatch.h"
> #include "smatch_slist.h"
> #include "smatch_extra.h"
>
> static int my_id;
>
> STATE(fresh);
>
> static int get_line(struct sm_state *sm)
> {
>         struct sm_state *tmp;
>         int line = 0;
>
>         FOR_EACH_PTR(sm->possible, tmp) {
>                 if (tmp->state == &undefined &&
>                     tmp->line > line)
>                         line = tmp->line;
>         } END_FOR_EACH_PTR(tmp);
>
>         if (!line)
>                 return sm->line;
>         return line;
> }
>
> static void match_modify(struct sm_state *sm, struct expression *mod_expr)
> {
>         if (sm->state != &fresh &&
>             mod_expr &&
>             mod_expr->type == EXPR_CALL &&
>             sym_name_is("kref_init", mod_expr->fn))
>                 sm_warning("kref has already been modifed (see line %d)", get_line(sm));
>
>         set_state(my_id, sm->name, sm->sym, &undefined);
> }
>
> static bool is_alloc(struct expression *expr)
> {
>         static struct expression *ignore, *alloc_expr;
>         struct expression *right;
>
>         if (!expr || expr->type != EXPR_ASSIGNMENT || expr->op != '=')
>                 return false;
>         if (expr == ignore)
>                 return false;
>         if (expr == alloc_expr)
>                 return true;
>         right = strip_expr(expr->right);
>         if (right->type == EXPR_CALL &&
>             (sym_name_is("kzalloc", right->fn) ||
>              sym_name_is("kmalloc", right->fn))) {
>                 alloc_expr = expr;
>                 return true;
>         }
>         ignore = expr;
>         return false;
> }
>
> static void match_assign(struct expression *expr)
> {
>         char *name;
>
>         if (!is_alloc(get_faked_expression()))
>                 return;
>         name = expr_to_str(expr->left);
>         if (name && strstr(name, "refcount.refs.counter"))
>                 set_state_expr(my_id, expr->left, &fresh);
>         free_string(name);
> }
>
> void check_kref_init_too_late(int id)
> {
>         my_id = id;
>
>         add_hook(&match_assign, ASSIGNMENT_HOOK_AFTER);
>         add_modification_hook(my_id, &match_modify);
> }
>
> --
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> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
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Re: [syzbot] KASAN: use-after-free Read in em28xx_close_extension

[Dan Carpenter]

On Tue, Jul 27, 2021 at 11:13:13PM +0800, Dongliang Mu wrote:
> On Tue, Jul 27, 2021 at 10:15 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > On Tue, Jul 27, 2021 at 06:01:51PM +0800, Hillf Danton wrote:
> > > Along the probe path,
> > >
> > > em28xx_usb_probe
> > >   dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> > >   retval = em28xx_init_dev(dev, udev, intf, nr);
> > >     em28xx_init_extension(dev);
> > >       em28xx_ir_init(struct em28xx *dev)
> > >         kref_get(&dev->ref);
> > >
> > >   kref_init(&dev->ref);
> >
> 
> Hi Dan,
> 
> I have developed a patch [1] to fix this crash. Would you like to help
> me double-check if it correctly fixes the underlying bug?
> 
> [1] [PATCH v2] [media] em28xx-input: fix refcount bug in
> em28xx_usb_disconnect  https://lkml.org/lkml/2021/7/19/263

No one likes to review patches which aren't sent over email...  :/
LKML.org doesn't give the message-id so I can't use b4 to download the
email.

That patch doesn't make any sense.  We call kref_get() at the start of
the function so we need to call kref_put() at the end.  The fact that
em28xx_ir_fini() calls kref_put() doesn't matter.  We will only call
fini if the init() succeeds (hopefully).  The em28xx_ir_init() error
handling is Ad Hoc Style but I don't see anything outright buggy.

I think Hillf's approach is correct.

regards,
dan carpenter

Re: [syzbot] KASAN: use-after-free Read in em28xx_close_extension

[Dan Carpenter]

On Tue, Jul 27, 2021 at 05:14:55PM +0300, Dan Carpenter wrote:
> On Tue, Jul 27, 2021 at 06:01:51PM +0800, Hillf Danton wrote:
> > Along the probe path,
> > 
> > em28xx_usb_probe
> >   dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> >   retval = em28xx_init_dev(dev, udev, intf, nr);
> >     em28xx_init_extension(dev);
> >       em28xx_ir_init(struct em28xx *dev)
> >         kref_get(&dev->ref);
> > 
> >   kref_init(&dev->ref);
> 
> Good detective work.
> 
> I've created a Smatch check to try find these.  It uses the fact that
> Smatch creates a bunch of fake assignments to set all the struct members
> of "dev" to zero.  Then it uses the modification hook to find the
> kref_init().  Those are sort of new uses for those hooks so that's quite
> fun.
> 
> I'll test it out overnight and see how it works.

My Smatch check didn't find any other bugs, but it only had 3 false
positives so I'll keep running it nightly on new code.

regards,
dan carpenter

Re: [syzbot] KASAN: use-after-free Read in em28xx_close_extension

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 0766ec82e5fb26fc5dc6d592bc61865608bdc651
Author: Stephen Brennan <stephen.s.brennan@oracle.com>
Date:   Wed Sep 1 17:51:41 2021 +0000

    namei: Fix use after free in kern_path_locked

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17bf2a03300000
start commit:   fa54d366a6e4 Merge tag 'acpi-5.14-rc7' of git://git.kernel..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=96f0602203250753
dashboard link: https://syzkaller.appspot.com/bug?extid=005037419ebdf14e1d87
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14c086c5300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12950bee300000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: namei: Fix use after free in kern_path_locked

For information about bisection process see: https://goo.gl/tpsmEJ#bisection