This is a note to let you know that I've just added the patch titled
uio: Fix use-after-free in uio_unregister_device()
to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 092561f06702dd4fdd7fb74dd3a838f1818529b7 Mon Sep 17 00:00:00 2001
From: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com Date: Mon, 2 Nov 2020 21:28:19 +0900 Subject: uio: Fix use-after-free in uio_unregister_device()
Commit 8fd0e2a6df26 ("uio: free uio id after uio file node is freed") triggered KASAN use-after-free failure at deletion of TCM-user backstores [1].
In uio_unregister_device(), struct uio_device *idev is passed to uio_free_minor() to refer idev->minor. However, before uio_free_minor() call, idev is already freed by uio_device_release() during call to device_unregister().
To avoid reference to idev->minor after idev free, keep idev->minor value in a local variable. Also modify uio_free_minor() argument to receive the value.
[1] BUG: KASAN: use-after-free in uio_unregister_device+0x166/0x190 Read of size 4 at addr ffff888105196508 by task targetcli/49158
CPU: 3 PID: 49158 Comm: targetcli Not tainted 5.10.0-rc1 #1 Hardware name: Supermicro Super Server/X10SRL-F, BIOS 2.0 12/17/2015 Call Trace: dump_stack+0xae/0xe5 ? uio_unregister_device+0x166/0x190 print_address_description.constprop.0+0x1c/0x210 ? uio_unregister_device+0x166/0x190 ? uio_unregister_device+0x166/0x190 kasan_report.cold+0x37/0x7c ? kobject_put+0x80/0x410 ? uio_unregister_device+0x166/0x190 uio_unregister_device+0x166/0x190 tcmu_destroy_device+0x1c4/0x280 [target_core_user] ? tcmu_release+0x90/0x90 [target_core_user] ? __mutex_unlock_slowpath+0xd6/0x5d0 target_free_device+0xf3/0x2e0 [target_core_mod] config_item_cleanup+0xea/0x210 configfs_rmdir+0x651/0x860 ? detach_groups.isra.0+0x380/0x380 vfs_rmdir.part.0+0xec/0x3a0 ? __lookup_hash+0x20/0x150 do_rmdir+0x252/0x320 ? do_file_open_root+0x420/0x420 ? strncpy_from_user+0xbc/0x2f0 ? getname_flags.part.0+0x8e/0x450 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f9e2bfc91fb Code: 73 01 c3 48 8b 0d 9d ec 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 54 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 6d ec 0c 00 f7 d8 64 89 01 48 RSP: 002b:00007ffdd2baafe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000054 RAX: ffffffffffffffda RBX: 00007f9e2beb44a0 RCX: 00007f9e2bfc91fb RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f9e1c20be90 RBP: 00007ffdd2bab000 R08: 0000000000000000 R09: 00007f9e2bdf2440 R10: 00007ffdd2baaf37 R11: 0000000000000246 R12: 00000000ffffff9c R13: 000055f9abb7e390 R14: 000055f9abcf9558 R15: 00007f9e2be7a780
Allocated by task 34735: kasan_save_stack+0x1b/0x40 __kasan_kmalloc.constprop.0+0xc2/0xd0 __uio_register_device+0xeb/0xd40 tcmu_configure_device+0x5a0/0xbc0 [target_core_user] target_configure_device+0x12f/0x760 [target_core_mod] target_dev_enable_store+0x32/0x50 [target_core_mod] configfs_write_file+0x2bb/0x450 vfs_write+0x1ce/0x610 ksys_write+0xe9/0x1b0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 49158: kasan_save_stack+0x1b/0x40 kasan_set_track+0x1c/0x30 kasan_set_free_info+0x1b/0x30 __kasan_slab_free+0x110/0x150 slab_free_freelist_hook+0x5a/0x170 kfree+0xc6/0x560 device_release+0x9b/0x210 kobject_put+0x13e/0x410 uio_unregister_device+0xf9/0x190 tcmu_destroy_device+0x1c4/0x280 [target_core_user] target_free_device+0xf3/0x2e0 [target_core_mod] config_item_cleanup+0xea/0x210 configfs_rmdir+0x651/0x860 vfs_rmdir.part.0+0xec/0x3a0 do_rmdir+0x252/0x320 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff888105196000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 1288 bytes inside of 2048-byte region [ffff888105196000, ffff888105196800) The buggy address belongs to the page: page:0000000098e6ca81 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x105190 head:0000000098e6ca81 order:3 compound_mapcount:0 compound_pincount:0 flags: 0x17ffffc0010200(slab|head) raw: 0017ffffc0010200 dead000000000100 dead000000000122 ffff888100043040 raw: 0000000000000000 0000000000080008 00000001ffffffff ffff88810eb55c01 page dumped because: kasan: bad access detected page->mem_cgroup:ffff88810eb55c01
Memory state around the buggy address: ffff888105196400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888105196480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888105196500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff888105196580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888105196600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: 8fd0e2a6df26 ("uio: free uio id after uio file node is freed") Cc: stable stable@vger.kernel.org Signed-off-by: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com Link: https://lore.kernel.org/r/20201102122819.2346270-1-shinichiro.kawasaki@wdc.c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/uio/uio.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index 6dca744e39e9..be06f1a961c2 100644 --- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -413,10 +413,10 @@ static int uio_get_minor(struct uio_device *idev) return retval; }
-static void uio_free_minor(struct uio_device *idev) +static void uio_free_minor(unsigned long minor) { mutex_lock(&minor_lock); - idr_remove(&uio_idr, idev->minor); + idr_remove(&uio_idr, minor); mutex_unlock(&minor_lock); }
@@ -990,7 +990,7 @@ int __uio_register_device(struct module *owner, err_uio_dev_add_attributes: device_del(&idev->dev); err_device_create: - uio_free_minor(idev); + uio_free_minor(idev->minor); put_device(&idev->dev); return ret; } @@ -1042,11 +1042,13 @@ EXPORT_SYMBOL_GPL(__devm_uio_register_device); void uio_unregister_device(struct uio_info *info) { struct uio_device *idev; + unsigned long minor;
if (!info || !info->uio_dev) return;
idev = info->uio_dev; + minor = idev->minor;
mutex_lock(&idev->info_lock); uio_dev_del_attributes(idev); @@ -1062,7 +1064,7 @@ void uio_unregister_device(struct uio_info *info)
device_unregister(&idev->dev);
- uio_free_minor(idev); + uio_free_minor(minor);
return; }