[PATCH 5.9 685/757] usb: gadget: function: printer: fix use-after-free in __lock_acquire

From: Greg Kroah-Hartman
Date: Tue Oct 27 2020 - 12:31:14 EST

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From: Zqiang <qiang.zhang@xxxxxxxxxxxxx>

[ Upstream commit e8d5f92b8d30bb4ade76494490c3c065e12411b1 ]

Fix this by increase object reference count.

BUG: KASAN: use-after-free in __lock_acquire+0x3fd4/0x4180
kernel/locking/lockdep.c:3831
Read of size 8 at addr ffff8880683b0018 by task syz-executor.0/3377

CPU: 1 PID: 3377 Comm: syz-executor.0 Not tainted 5.6.11 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xce/0x128 lib/dump_stack.c:118
print_address_description.constprop.4+0x21/0x3c0 mm/kasan/report.c:374
__kasan_report+0x131/0x1b0 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:641
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
__lock_acquire+0x3fd4/0x4180 kernel/locking/lockdep.c:3831
lock_acquire+0x127/0x350 kernel/locking/lockdep.c:4488
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159
printer_ioctl+0x4a/0x110 drivers/usb/gadget/function/f_printer.c:723
vfs_ioctl fs/ioctl.c:47 [inline]
ksys_ioctl+0xfb/0x130 fs/ioctl.c:763
__do_sys_ioctl fs/ioctl.c:772 [inline]
__se_sys_ioctl fs/ioctl.c:770 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4531a9
Code: ed 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48
89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
01 f0 ff ff 0f 83 bb 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd14ad72c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000073bfa8 RCX: 00000000004531a9
RDX: fffffffffffffff9 RSI: 000000000000009e RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004bbd61
R13: 00000000004d0a98 R14: 00007fd14ad736d4 R15: 00000000ffffffff

Allocated by task 2393:
save_stack+0x21/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc.constprop.3+0xa7/0xd0 mm/kasan/common.c:515
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
kmem_cache_alloc_trace+0xfa/0x2d0 mm/slub.c:2813
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
gprinter_alloc+0xa1/0x870 drivers/usb/gadget/function/f_printer.c:1416
usb_get_function+0x58/0xc0 drivers/usb/gadget/functions.c:61
config_usb_cfg_link+0x1ed/0x3e0 drivers/usb/gadget/configfs.c:444
configfs_symlink+0x527/0x11d0 fs/configfs/symlink.c:202
vfs_symlink+0x33d/0x5b0 fs/namei.c:4201
do_symlinkat+0x11b/0x1d0 fs/namei.c:4228
__do_sys_symlinkat fs/namei.c:4242 [inline]
__se_sys_symlinkat fs/namei.c:4239 [inline]
__x64_sys_symlinkat+0x73/0xb0 fs/namei.c:4239
do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 3368:
save_stack+0x21/0x90 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0x135/0x190 mm/kasan/common.c:476
kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
slab_free_hook mm/slub.c:1444 [inline]
slab_free_freelist_hook mm/slub.c:1477 [inline]
slab_free mm/slub.c:3034 [inline]
kfree+0xf7/0x410 mm/slub.c:3995
gprinter_free+0x49/0xd0 drivers/usb/gadget/function/f_printer.c:1353
usb_put_function+0x38/0x50 drivers/usb/gadget/functions.c:87
config_usb_cfg_unlink+0x2db/0x3b0 drivers/usb/gadget/configfs.c:485
configfs_unlink+0x3b9/0x7f0 fs/configfs/symlink.c:250
vfs_unlink+0x287/0x570 fs/namei.c:4073
do_unlinkat+0x4f9/0x620 fs/namei.c:4137
__do_sys_unlink fs/namei.c:4184 [inline]
__se_sys_unlink fs/namei.c:4182 [inline]
__x64_sys_unlink+0x42/0x50 fs/namei.c:4182
do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880683b0000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 24 bytes inside of
1024-byte region [ffff8880683b0000, ffff8880683b0400)
The buggy address belongs to the page:
page:ffffea0001a0ec00 refcount:1 mapcount:0 mapping:ffff88806c00e300
index:0xffff8880683b1800 compound_mapcount: 0
flags: 0x100000000010200(slab|head)
raw: 0100000000010200 0000000000000000 0000000600000001 ffff88806c00e300
raw: ffff8880683b1800 000000008010000a 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Reported-by: Kyungtae Kim <kt0755@xxxxxxxxx>
Signed-off-by: Zqiang <qiang.zhang@xxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <balbi@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/usb/gadget/function/f_printer.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 68697f596066c..64a4112068fc8 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -31,6 +31,7 @@
#include <linux/types.h>
#include <linux/ctype.h>
#include <linux/cdev.h>
+#include <linux/kref.h>

#include <asm/byteorder.h>
#include <linux/io.h>
@@ -64,7 +65,7 @@ struct printer_dev {
struct usb_gadget *gadget;
s8 interface;
struct usb_ep *in_ep, *out_ep;
-
+ struct kref kref;
struct list_head rx_reqs; /* List of free RX structs */
struct list_head rx_reqs_active; /* List of Active RX xfers */
struct list_head rx_buffers; /* List of completed xfers */
@@ -218,6 +219,13 @@ static inline struct usb_endpoint_descriptor *ep_desc(struct usb_gadget *gadget,

/*-------------------------------------------------------------------------*/

+static void printer_dev_free(struct kref *kref)
+{
+ struct printer_dev *dev = container_of(kref, struct printer_dev, kref);
+
+ kfree(dev);
+}
+
static struct usb_request *
printer_req_alloc(struct usb_ep *ep, unsigned len, gfp_t gfp_flags)
{
@@ -353,6 +361,7 @@ printer_open(struct inode *inode, struct file *fd)

spin_unlock_irqrestore(&dev->lock, flags);

+ kref_get(&dev->kref);
DBG(dev, "printer_open returned %x\n", ret);
return ret;
}
@@ -370,6 +379,7 @@ printer_close(struct inode *inode, struct file *fd)
dev->printer_status &= ~PRINTER_SELECTED;
spin_unlock_irqrestore(&dev->lock, flags);

+ kref_put(&dev->kref, printer_dev_free);
DBG(dev, "printer_close\n");

return 0;
@@ -1386,7 +1396,8 @@ static void gprinter_free(struct usb_function *f)
struct f_printer_opts *opts;

opts = container_of(f->fi, struct f_printer_opts, func_inst);
- kfree(dev);
+
+ kref_put(&dev->kref, printer_dev_free);
mutex_lock(&opts->lock);
--opts->refcnt;
mutex_unlock(&opts->lock);
@@ -1455,6 +1466,7 @@ static struct usb_function *gprinter_alloc(struct usb_function_instance *fi)
return ERR_PTR(-ENOMEM);
}

+ kref_init(&dev->kref);
++opts->refcnt;
dev->minor = opts->minor;
dev->pnp_string = opts->pnp_string;
--
2.25.1

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