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Date:   Sat, 3 Apr 2021 09:06:22 +0200
From:   Greg KH <greg@kroah.com>
To:     Zheyu Ma <zheyuma97@gmail.com>
Cc:     stefanr@s5r6.in-berlin.de, linux1394-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, security@kernel.org
Subject: Re: [PATCH] firewire: nosy: Fix a use-after-free bug in nosy_ioctl()
Message-ID: <YGgT7oQy7RIU7X2d@kroah.com>
References: <1617433116-5930-1-git-send-email-zheyuma97@gmail.com>
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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@gmail.com>
> Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
> ---
>  drivers/firewire/nosy.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

Looks good:

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>