From: Genjian Zhang zhanggenjian@kylinos.cn
Hello!
We found that 2035c770bfdb ("loop: Check for overflow while configuring loop") lost a unlock loop_ctl_mutex in loop_get_status(...). which caused syzbot to report a UAF issue. However, the upstream patch does not have this issue. So, we revert this patch and directly apply the unmodified upstream patch.
Risk use-after-free as reported by syzbot：
[ 174.437352] BUG: KASAN: use-after-free in __mutex_lock.isra.10+0xbc4/0xc30 [ 174.437772] Read of size 4 at addr ffff8880bac49ab8 by task syz-executor.0/13897 [ 174.438205] [ 174.438306] CPU: 1 PID: 13897 Comm: syz-executor.0 Not tainted 4.19.306 #1 [ 174.438712] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1kylin1 04/01/2014 [ 174.439236] Call Trace: [ 174.439392] dump_stack+0x94/0xc7 [ 174.439596] ? __mutex_lock.isra.10+0xbc4/0xc30 [ 174.439881] print_address_description+0x60/0x229 [ 174.440165] ? __mutex_lock.isra.10+0xbc4/0xc30 [ 174.440436] kasan_report.cold.6+0x241/0x2fd [ 174.440696] __mutex_lock.isra.10+0xbc4/0xc30 [ 174.440959] ? entry_SYSCALL_64_after_hwframe+0x5c/0xc1 [ 174.441272] ? mutex_trylock+0xa0/0xa0 [ 174.441500] ? entry_SYSCALL_64_after_hwframe+0x5c/0xc1 [ 174.441816] ? kobject_get_unless_zero+0x129/0x1c0 [ 174.442106] ? kset_unregister+0x30/0x30 [ 174.442351] ? find_symbol_in_section+0x310/0x310 [ 174.442634] ? __mutex_lock_slowpath+0x10/0x10 [ 174.442901] mutex_lock_killable+0xb0/0xf0 [ 174.443149] ? __mutex_lock_killable_slowpath+0x10/0x10 [ 174.443465] ? __mutex_lock_slowpath+0x10/0x10 [ 174.443732] ? _cond_resched+0x10/0x20 [ 174.443966] ? kobject_get+0x54/0xa0 [ 174.444190] lo_open+0x16/0xc0 [ 174.444382] __blkdev_get+0x273/0x10f0 [ 174.444612] ? lo_fallocate.isra.20+0x150/0x150 [ 174.444886] ? bdev_disk_changed+0x190/0x190 [ 174.445146] ? path_init+0x1030/0x1030 [ 174.445371] ? do_syscall_64+0x9a/0x2d0 [ 174.445608] ? deref_stack_reg+0xab/0xe0 [ 174.445852] blkdev_get+0x97/0x880 [ 174.446061] ? walk_component+0x297/0xdc0 [ 174.446303] ? __blkdev_get+0x10f0/0x10f0 [ 174.446547] ? __fsnotify_inode_delete+0x20/0x20 [ 174.446822] blkdev_open+0x1bd/0x240 [ 174.447040] do_dentry_open+0x448/0xf80 [ 174.447274] ? blkdev_get_by_dev+0x60/0x60 [ 174.447522] ? __x64_sys_fchdir+0x1a0/0x1a0 [ 174.447775] ? inode_permission+0x86/0x320 [ 174.448022] path_openat+0xa83/0x3ed0 [ 174.448248] ? path_mountpoint+0xb50/0xb50 [ 174.448495] ? kasan_kmalloc+0xbf/0xe0 [ 174.448723] ? kmem_cache_alloc+0xbc/0x1b0 [ 174.448971] ? getname_flags+0xc4/0x560 [ 174.449203] ? do_sys_open+0x1ce/0x3f0 [ 174.449432] ? do_syscall_64+0x9a/0x2d0 [ 174.449706] ? entry_SYSCALL_64_after_hwframe+0x5c/0xc1 [ 174.450022] ? __d_alloc+0x2a/0xa50 [ 174.450232] ? kasan_unpoison_shadow+0x30/0x40 [ 174.450510] ? should_fail+0x117/0x6c0 [ 174.450737] ? timespec64_trunc+0xc1/0x150 [ 174.450986] ? inode_init_owner+0x2e0/0x2e0 [ 174.451237] ? timespec64_trunc+0xc1/0x150 [ 174.451484] ? inode_init_owner+0x2e0/0x2e0 [ 174.451736] do_filp_open+0x197/0x270 [ 174.451959] ? may_open_dev+0xd0/0xd0 [ 174.452182] ? kasan_unpoison_shadow+0x30/0x40 [ 174.452448] ? kasan_kmalloc+0xbf/0xe0 [ 174.452672] ? __alloc_fd+0x1a3/0x4b0 [ 174.452895] do_sys_open+0x2c7/0x3f0 [ 174.453114] ? filp_open+0x60/0x60 [ 174.453320] do_syscall_64+0x9a/0x2d0 [ 174.453541] ? prepare_exit_to_usermode+0xf3/0x170 [ 174.453832] entry_SYSCALL_64_after_hwframe+0x5c/0xc1 [ 174.454136] RIP: 0033:0x41edee [ 174.454321] Code: 25 00 00 41 00 3d 00 00 41 00 74 48 48 c7 c0 a4 af 0b 01 8b 00 85 c0 75 69 89 f2 b8 01 01 00 00 48 89 fe bf 9c ff ff ff 0f 05 <48> 3d 00 f0 ff ff 0f 87 a6 00 00 00 48 8b 4c 24 28 64 48 33 0c5 [ 174.455404] RSP: 002b:00007ffd2501fbd0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 [ 174.455854] RAX: ffffffffffffffda RBX: 00007ffd2501fc90 RCX: 000000000041edee [ 174.456273] RDX: 0000000000000002 RSI: 00007ffd2501fcd0 RDI: 00000000ffffff9c [ 174.456698] RBP: 0000000000000003 R08: 0000000000000001 R09: 00007ffd2501f9a7 [ 174.457116] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 [ 174.457535] R13: 0000000000565e48 R14: 00007ffd2501fcd0 R15: 0000000000400510 [ 174.457955] [ 174.458052] Allocated by task 945: [ 174.458261] kasan_kmalloc+0xbf/0xe0 [ 174.458478] kmem_cache_alloc_node+0xb4/0x1d0 [ 174.458743] copy_process.part.57+0x14b0/0x7010 [ 174.459017] _do_fork+0x197/0x980 [ 174.459218] kernel_thread+0x2f/0x40 [ 174.459438] call_usermodehelper_exec_work+0xa8/0x240 [ 174.459742] process_one_work+0x933/0x13b0 [ 174.459986] worker_thread+0x8c/0x1000 [ 174.460212] kthread+0x343/0x410 [ 174.460408] ret_from_fork+0x35/0x40 [ 174.460621] [ 174.460716] Freed by task 22902: [ 174.460913] __kasan_slab_free+0x125/0x170 [ 174.461159] kmem_cache_free+0x6e/0x1b0 [ 174.461391] __put_task_struct+0x1c4/0x440 [ 174.461636] delayed_put_task_struct+0x135/0x170 [ 174.461915] rcu_process_callbacks+0x578/0x15c0 [ 174.462184] __do_softirq+0x175/0x60e [ 174.462403] [ 174.462501] The buggy address belongs to the object at ffff8880bac49a80 [ 174.462501] which belongs to the cache task_struct of size 3264 [ 174.463235] The buggy address is located 56 bytes inside of [ 174.463235] 3264-byte region [ffff8880bac49a80, ffff8880bac4a740) [ 174.463923] The buggy address belongs to the page: [ 174.464210] page:ffffea0002eb1200 count:1 mapcount:0 mapping:ffff888188ca0a00 index:0x0 compound_mapcount: 0 [ 174.464784] flags: 0x100000000008100(slab|head) [ 174.465079] raw: 0100000000008100 ffffea0002eaa400 0000000400000004 ffff888188ca0a00 [ 174.465533] raw: 0000000000000000 0000000000090009 00000001ffffffff 0000000000000000 [ 174.465988] page dumped because: kasan: bad access detected [ 174.466321] [ 174.466322] Memory state around the buggy address: [ 174.466325] ffff8880bac49980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 174.466327] ffff8880bac49a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 174.466329] >ffff8880bac49a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 174.466329] ^ [ 174.466331] ffff8880bac49b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 174.466333] ffff8880bac49b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 174.466333] ================================================================== [ 174.466338] Disabling lock debugging due to kernel taint
Best regards Genjian
Genjian Zhang (1): Revert "loop: Check for overflow while configuring loop"
Holger Hoffstätte (1): loop: properly observe rotational flag of underlying device
Martijn Coenen (5): loop: Call loop_config_discard() only after new config is applied loop: Remove sector_t truncation checks loop: Factor out setting loop device size loop: Refactor loop_set_status() size calculation loop: Factor out configuring loop from status
Siddh Raman Pant (1): loop: Check for overflow while configuring loop
Zhong Jinghua (1): loop: loop_set_status_from_info() check before assignment
drivers/block/loop.c | 204 ++++++++++++++++++++++++++----------------- 1 file changed, 123 insertions(+), 81 deletions(-)