[PATCH 5.4 098/215] Revert "loop: Check for overflow while configuring loop"

Greg Kroah-Hartman
2024-04-11T10:18:53Z

From: Genjian Zhang <zhanggenjian@kylinos.cn>

This reverts commit 13b2856037a651ba3ab4a8b25ecab3e791926da3.

This patch lost a unlock loop_ctl_mutex in loop_get_status(...),
which caused syzbot to report a UAF issue.The upstream patch does not
have this issue. Therefore, we revert this patch and directly apply
the upstream patch later on.

Risk use-after-free as reported by syzbot：

[ 84.669496] ==================================================================
[ 84.670021] BUG: KASAN: use-after-free in __mutex_lock.isra.9+0xc13/0xcb0
[ 84.670433] Read of size 4 at addr ffff88808dba43b8 by task syz-executor.22/14230
[ 84.670885]
[ 84.670987] CPU: 1 PID: 14230 Comm: syz-executor.22 Not tainted 5.4.270 #4
[ 84.671397] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1kylin1 04/01/2014
[ 84.671927] Call Trace:
[ 84.672085] dump_stack+0x94/0xc7
[ 84.672293] ? __mutex_lock.isra.9+0xc13/0xcb0
[ 84.672569] print_address_description.constprop.6+0x16/0x220
[ 84.672915] ? __mutex_lock.isra.9+0xc13/0xcb0
[ 84.673187] ? __mutex_lock.isra.9+0xc13/0xcb0
[ 84.673462] __kasan_report.cold.9+0x1a/0x32
[ 84.673723] ? __mutex_lock.isra.9+0xc13/0xcb0
[ 84.673993] kasan_report+0x10/0x20
[ 84.674208] __mutex_lock.isra.9+0xc13/0xcb0
[ 84.674468] ? __mutex_lock.isra.9+0x617/0xcb0
[ 84.674739] ? ww_mutex_lock_interruptible+0x100/0x100
[ 84.675055] ? ww_mutex_lock_interruptible+0x100/0x100
[ 84.675369] ? kobject_get_unless_zero+0x144/0x190
[ 84.675668] ? kobject_del+0x60/0x60
[ 84.675893] ? __module_get+0x120/0x120
[ 84.676128] ? __mutex_lock_slowpath+0x10/0x10
[ 84.676399] mutex_lock_killable+0xde/0xf0
[ 84.676652] ? __mutex_lock_killable_slowpath+0x10/0x10
[ 84.676967] ? __mutex_lock_slowpath+0x10/0x10
[ 84.677243] ? disk_block_events+0x1d/0x120
[ 84.677509] lo_open+0x16/0xc0
[ 84.677701] ? lo_compat_ioctl+0x160/0x160
[ 84.677954] __blkdev_get+0xb0f/0x1160
[ 84.678185] ? bd_may_claim+0xd0/0xd0
[ 84.678410] ? bdev_disk_changed+0x190/0x190
[ 84.678674] ? _raw_spin_lock+0x7c/0xd0
[ 84.678915] ? _raw_write_lock_bh+0xd0/0xd0
[ 84.679172] blkdev_get+0x9b/0x290
[ 84.679381] ? ihold+0x1a/0x40
[ 84.679574] blkdev_open+0x1bd/0x240
[ 84.679794] do_dentry_open+0x439/0x1000
[ 84.680035] ? blkdev_get_by_dev+0x60/0x60
[ 84.680286] ? __x64_sys_fchdir+0x1a0/0x1a0
[ 84.680557] ? inode_permission+0x86/0x320
[ 84.680814] path_openat+0x998/0x4120
[ 84.681044] ? stack_trace_consume_entry+0x160/0x160
[ 84.681348] ? do_futex+0x136/0x1880
[ 84.681568] ? path_mountpoint+0xb50/0xb50
[ 84.681823] ? save_stack+0x4d/0x80
[ 84.682038] ? save_stack+0x19/0x80
[ 84.682253] ? __kasan_kmalloc.constprop.6+0xc1/0xd0
[ 84.682553] ? kmem_cache_alloc+0xc7/0x210
[ 84.682804] ? getname_flags+0xc4/0x560
[ 84.683045] ? do_sys_open+0x1ce/0x450
[ 84.683272] ? do_syscall_64+0x9a/0x330
[ 84.683509] ? entry_SYSCALL_64_after_hwframe+0x5c/0xc1
[ 84.683826] ? _raw_spin_lock+0x7c/0xd0
[ 84.684063] ? _raw_write_lock_bh+0xd0/0xd0
[ 84.684319] ? futex_exit_release+0x60/0x60
[ 84.684574] ? kasan_unpoison_shadow+0x30/0x40
[ 84.684844] ? __kasan_kmalloc.constprop.6+0xc1/0xd0
[ 84.685149] ? get_partial_node.isra.83.part.84+0x1e5/0x340
[ 84.685485] ? __fget_light+0x1d1/0x550
[ 84.685721] do_filp_open+0x197/0x270
[ 84.685946] ? may_open_dev+0xd0/0xd0
[ 84.686172] ? kasan_unpoison_shadow+0x30/0x40
[ 84.686443] ? __kasan_kmalloc.constprop.6+0xc1/0xd0
[ 84.686743] ? __alloc_fd+0x1a3/0x580
[ 84.686973] do_sys_open+0x2c7/0x450
[ 84.687195] ? filp_open+0x60/0x60
[ 84.687406] ? __x64_sys_timer_settime32+0x280/0x280
[ 84.687707] do_syscall_64+0x9a/0x330
[ 84.687931] ? syscall_return_slowpath+0x17a/0x230
[ 84.688221] entry_SYSCALL_64_after_hwframe+0x5c/0xc1
[ 84.688524]
[ 84.688622] Allocated by task 14056:
[ 84.688842] save_stack+0x19/0x80
[ 84.689044] __kasan_kmalloc.constprop.6+0xc1/0xd0
[ 84.689333] kmem_cache_alloc_node+0xe2/0x230
[ 84.689600] copy_process+0x165c/0x72d0
[ 84.689833] _do_fork+0xf9/0x9a0
[ 84.690032] __x64_sys_clone+0x17a/0x200
[ 84.690271] do_syscall_64+0x9a/0x330
[ 84.690496] entry_SYSCALL_64_after_hwframe+0x5c/0xc1
[ 84.690800]
[ 84.690903] Freed by task 0:
[ 84.691081] save_stack+0x19/0x80
[ 84.691287] __kasan_slab_free+0x125/0x170
[ 84.691535] kmem_cache_free+0x7a/0x2a0
[ 84.691774] __put_task_struct+0x1ec/0x4a0
[ 84.692023] delayed_put_task_struct+0x178/0x1d0
[ 84.692303] rcu_core+0x538/0x16c0
[ 84.692512] __do_softirq+0x175/0x63d
[ 84.692741]
[ 84.692840] The buggy address belongs to the object at ffff88808dba4380
[ 84.692840] which belongs to the cache task_struct of size 3328
[ 84.693584] The buggy address is located 56 bytes inside of
[ 84.693584] 3328-byte region [ffff88808dba4380, ffff88808dba5080)
[ 84.694272] The buggy address belongs to the page:
[ 84.694563] page:ffffea000236e800 refcount:1 mapcount:0 mapping:ffff8881838acdc0 index:0x0 compound_mapcount: 0
[ 84.695166] flags: 0x100000000010200(slab|head)
[ 84.695457] raw: 0100000000010200 dead000000000100 dead000000000122 ffff8881838acdc0
[ 84.695919] raw: 0000000000000000 0000000000090009 00000001ffffffff 0000000000000000
[ 84.696375] page dumped because: kasan: bad access detected
[ 84.696705]
[ 84.696801] Memory state around the buggy address:
[ 84.697089] ffff88808dba4280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 84.697519] ffff88808dba4300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 84.697945] >ffff88808dba4380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 84.698371] ^
[ 84.698674] ffff88808dba4400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 84.699111] ffff88808dba4480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 84.699537] ==================================================================
[ 84.699965] Disabling lock debugging due to kernel taint

Reported-by: k2ci <kernel-bot@kylinos.cn>
Signed-off-by: Genjian Zhang <zhanggenjian@kylinos.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/block/loop.c | 5 -----
1 file changed, 5 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1397,11 +1397,6 @@ loop_get_status(struct loop_device *lo,
info->lo_number = lo->lo_number;
info->lo_offset = lo->lo_offset;
info->lo_sizelimit = lo->lo_sizelimit;
-
- /* loff_t vars have been assigned __u64 */
- if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
- return -EOVERFLOW;
-
info->lo_flags = lo->lo_flags;
memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);