media: dvbdev: keep dvb device ref balanced in dvb generic release and open

Commit Message

Edward Adam Davis Jan. 19, 2025, 3:42 a.m. UTC

syzbot report a slab-use-after-free Read in dvb_device_open. [1]

The dvb device have been putted by dvb_generic_release() in dvb_frontend_open()
and have been freed in dvb_device_open() by dvb_device_put().

[1]
BUG: KASAN: slab-use-after-free in dvb_device_open+0x36a/0x3b0 drivers/media/dvb-core/dvbdev.c:99
Read of size 8 at addr ffff8881476baa18 by task syz-executor353/9116

CPU: 1 UID: 0 PID: 9116 Comm: syz-executor353 Not tainted 6.13.0-rc7-syzkaller-00189-g595523945be0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:489
 kasan_report+0xd9/0x110 mm/kasan/report.c:602
 dvb_device_open+0x36a/0x3b0 drivers/media/dvb-core/dvbdev.c:99
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0xf59/0x1ea0 fs/open.c:945
 vfs_open+0x82/0x3f0 fs/open.c:1075
 do_open fs/namei.c:3828 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3987
 do_filp_open+0x20c/0x470 fs/namei.c:4014
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
 do_sys_open fs/open.c:1417 [inline]
 __do_sys_openat fs/open.c:1433 [inline]
 __se_sys_openat fs/open.c:1428 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1428
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbafad2db29
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff3ae8be88 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbafad2db29
RDX: 0000000000000001 RSI: 0000000020000000 RDI: ffffffffffffff9c
RBP: 00000000000f4240 R08: 0000000000008000 R09: 0000000000008000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000015edd
R13: 00007fff3ae8beac R14: 00007fff3ae8bec0 R15: 00007fff3ae8beb0
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kmalloc_noprof include/linux/slab.h:901 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 dvb_register_device+0x1e2/0x2380 drivers/media/dvb-core/dvbdev.c:475
 dvb_register_frontend+0x5a7/0x880 drivers/media/dvb-core/dvb_frontend.c:3051
 vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:430 [inline]
 vidtv_bridge_probe+0x45e/0xa90 drivers/media/test-drivers/vidtv/vidtv_bridge.c:502
 platform_probe+0xff/0x1f0 drivers/base/platform.c:1404
 call_driver_probe drivers/base/dd.c:579 [inline]
 really_probe+0x23e/0xa90 drivers/base/dd.c:658
 __driver_probe_device+0x1de/0x440 drivers/base/dd.c:800
 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:830
 __driver_attach+0x283/0x580 drivers/base/dd.c:1216
 bus_for_each_dev+0x13c/0x1d0 drivers/base/bus.c:370
 bus_add_driver+0x2e9/0x690 drivers/base/bus.c:675
 driver_register+0x15c/0x4b0 drivers/base/driver.c:246
 vidtv_bridge_init+0x45/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:592
 do_one_initcall+0x128/0x630 init/main.c:1266
 do_initcall_level init/main.c:1328 [inline]
 do_initcalls init/main.c:1344 [inline]
 do_basic_setup init/main.c:1363 [inline]
 kernel_init_freeable+0x58f/0x8b0 init/main.c:1577
 kernel_init+0x1c/0x2b0 init/main.c:1466
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 9110:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2353 [inline]
 slab_free mm/slub.c:4613 [inline]
 kfree+0x14f/0x4b0 mm/slub.c:4761
 dvb_free_device drivers/media/dvb-core/dvbdev.c:619 [inline]
 kref_put include/linux/kref.h:65 [inline]
 dvb_device_put.part.0+0x60/0x90 drivers/media/dvb-core/dvbdev.c:632
 dvb_device_put drivers/media/dvb-core/dvbdev.c:631 [inline]
 dvb_device_open+0x2a4/0x3b0 drivers/media/dvb-core/dvbdev.c:113
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0xf59/0x1ea0 fs/open.c:945
 vfs_open+0x82/0x3f0 fs/open.c:1075
 do_open fs/namei.c:3828 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3987
 do_filp_open+0x20c/0x470 fs/namei.c:4014
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
 do_sys_open fs/open.c:1417 [inline]
 __do_sys_openat fs/open.c:1433 [inline]
 __se_sys_openat fs/open.c:1428 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1428
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported-by: [e-mail]
Closes: https://syzkaller.appspot.com/bug?extid=1eb177ecc3943b883f0a
Tested-by: [e-mail]
Signed-off-by: Edward Adam Davis <[e-mail]>
---
 drivers/media/dvb-core/dvb_frontend.c | 1 +
 drivers/media/dvb-core/dvbdev.c       | 1 +
 2 files changed, 2 insertions(+)

Patch

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index a05aa271a1ba..738b63255e5c 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -2873,6 +2873,7 @@  static int dvb_frontend_open(struct inode *inode, struct file *file)
 
 	if (adapter->mfe_shared)
 		mutex_unlock(&adapter->mfe_lock);
+	dvb_generic_release(inode, file);
 	return ret;
 
 err3:
diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index 9df7c213716a..d17f08adf443 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -148,6 +148,7 @@  int dvb_generic_open(struct inode *inode, struct file *file)
 	}
 
 	dvbdev->users--;
+	dvb_device_get(dvbdev);
 	return 0;
 }
 EXPORT_SYMBOL(dvb_generic_open);