Re: [PATCH] firewire: nosy: Fix a use-after-free bug in nosy_ioctl()

From: Greg KH
Date: Sat Apr 03 2021 - 03:09:38 EST

On Sat, Apr 03, 2021 at 06:58:36AM +0000, Zheyu Ma wrote:
> For each device, the nosy driver allocates a pcilynx structure.
> A use-after-free might happen in the following scenario:
>
> 1. Open nosy device for the first time and call ioctl with command
> NOSY_IOC_START, then a new client A will be malloced and added
> to doubly linked list.
> 2. Open nosy device for the second time and call ioctl with command
> NOSY_IOC_START, then a new client B will be malloced and added
> to doubly linked list.
> 3. Call ioctl with command NOSY_IOC_START for client A, then client A
> will be readded to the doubly linked list. Now the doubly linked
> list is messed up.
> 4. Close the first nosy device and nosy_release will be called.
> In nosy_release, client A will be unlinked and freed.
> 5. Close the second nosy device, and client A will be referenced,
> resulting in UAF.
>
> The root cause of this bug is that the element in the doubly linked list
> is reentered into the list.
> Fix this bug by adding a check before inserting a client. If a client
> is already in the linked list, don't insert it.
>
> The following KASAN report reveals it:
>
> [ 14.672676 ] BUG: KASAN: use-after-free in nosy_release+0x1ea/0x210
> [ 14.673113 ] Write of size 8 at addr ffff888102ad7360 by task poc
> [ 14.673609 ] CPU: 3 PID: 337 Comm: poc Not tainted 5.12.0-rc5+ #6
> [ 14.673988 ] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> [ 14.674686 ] Call Trace:
> [ 14.674843 ] dump_stack+0x8a/0xb5
> [ 14.675061 ] print_address_description.constprop.0+0x18/0x130
> [ 14.675428 ] ? nosy_release+0x1ea/0x210
> [ 14.675676 ] ? nosy_release+0x1ea/0x210
> [ 14.675916 ] kasan_report.cold+0x7f/0x111
> [ 14.676169 ] ? nosy_release+0x1ea/0x210
> [ 14.676409 ] nosy_release+0x1ea/0x210
> [ 14.676642 ] __fput+0x1e2/0x840
> [ 14.676844 ] task_work_run+0xe8/0x180
> [ 14.677083 ] exit_to_user_mode_prepare+0x114/0x120
> [ 14.677388 ] syscall_exit_to_user_mode+0x1d/0x40
> [ 14.677678 ] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 14.677995 ] RIP: 0033:0x7fc5a8666f30
> [ 14.678229 ] Code: 00 64 c7 00 0d 00 00 00 b8 ff ff ff ff eb 90
> b8 ff ff ff ff eb 89 0f 1f 40 00 83 3d d9 27 2c 00 00 75 10 b8 03
> 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e84
> [ 14.679385 ] RSP: 002b:00007ffe9e94cd68 EFLAGS: 00000246
> ORIG_RAX: 0000000000000003
> [ 14.679862 ] RAX: 0000000000000000 RBX: 0000000000000000
> RCX: 00007fc5a8666f30
> [ 14.680301 ] RDX: 00007ffe9e94ce78 RSI: 0000000000002601
> RDI: 0000000000000004
> [ 14.680743 ] RBP: 00007ffe9e94cd80 R08: 0000564727400850
> R09: 00007fc5a8939ba0
> [ 14.681180 ] R10: 0000000000000692 R11: 0000000000000246
> R12: 0000564727400610
> [ 14.681624 ] R13: 00007ffe9e94ce60 R14: 0000000000000000
> R15: 0000000000000000
> [ 14.682072 ]
> [ 14.682168 ] Allocated by task 337:
> [ 14.682387 ] kasan_save_stack+0x1b/0x40
> [ 14.682633 ] __kasan_kmalloc+0x7a/0x90
> [ 14.682868 ] nosy_open+0x154/0x4d0
> [ 14.683089 ] misc_open+0x2ec/0x410
> [ 14.683313 ] chrdev_open+0x20d/0x5a0
> [ 14.683541 ] do_dentry_open+0x40f/0xe80
> [ 14.683787 ] path_openat+0x1cf9/0x37b0
> [ 14.684025 ] do_filp_open+0x16d/0x390
> [ 14.684253 ] do_sys_openat2+0x11d/0x360
> [ 14.684497 ] __x64_sys_open+0xfd/0x1a0
> [ 14.684736 ] do_syscall_64+0x33/0x40
> [ 14.684964 ] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 14.685283 ]
> [ 14.685384 ] Freed by task 337:
> [ 14.685580 ] kasan_save_stack+0x1b/0x40
> [ 14.685822 ] kasan_set_track+0x1c/0x30
> [ 14.686062 ] kasan_set_free_info+0x20/0x30
> [ 14.686324 ] __kasan_slab_free+0xe5/0x110
> [ 14.686581 ] kfree+0x8f/0x210
> [ 14.686775 ] nosy_release+0x158/0x210
> [ 14.687011 ] __fput+0x1e2/0x840
> [ 14.687213 ] task_work_run+0xe8/0x180
> [ 14.687449 ] exit_to_user_mode_prepare+0x114/0x120
> [ 14.687750 ] syscall_exit_to_user_mode+0x1d/0x40
> [ 14.688040 ] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 14.688356 ]
> [ 14.688454 ] The buggy address belongs to the object at
> ffff888102ad7300
> [ 14.688454 ] which belongs to the cache kmalloc-128 of size 128
> [ 14.689232 ] The buggy address is located 96 bytes inside of
> [ 14.689232 ] 128-byte region [ffff888102ad7300, ffff888102ad7380)
> [ 14.689955 ] The buggy address belongs to the page:
> [ 14.690258 ] page:0000000046ca3dc1 refcount:1 mapcount:0
> mapping:0000000000000000 index:0xffff888102ad7100 pfn:0x102ad6
> [ 14.690917 ] head:0000000046ca3dc1 order:1 compound_mapcount:0
> [ 14.691278 ] flags: 0x200000000010200(slab|head)
> [ 14.691562 ] raw: 0200000000010200 dead000000000100
> dead000000000122 ffff8881000428c0
> [ 14.692044 ] raw: ffff888102ad7100 0000000080200013
> 00000001ffffffff 0000000000000000
> [ 14.692531 ] page dumped because: kasan: bad access detected
> [ 14.692877 ]
> [ 14.692978 ] Memory state around the buggy address:
> [ 14.693282 ] ffff888102ad7200: fa fb fb fb fb fb fb fb fb fb
> fb fb fb fb fb fb
> [ 14.693737 ] ffff888102ad7280: fc fc fc fc fc fc fc fc fc fc
> fc fc fc fc fc fc
> [ 14.694191 ] >ffff888102ad7300: fa fb fb fb fb fb fb fb fb fb
> fb fb fb fb fb fb
> [ 14.695061 ] ffff888102ad7380: fc fc fc fc fc fc fc fc fc fc
> fc fc fc fc fc fc
> [ 14.695518 ] ffff888102ad7400: 00 00 00 00 00 00 00 00 00 00
> 00 00 00 00 fc fc
> [ 14.695964 ]
> ==================================================================]
>
> Reported-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
> Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
> ---
> drivers/firewire/nosy.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)

Looks good:

Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>