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SubjectRe: [PATCH] kretprobe: check re-registration of the same kretprobe earlier
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On 2020/3/6 23:21, Masami Hiramatsu wrote:
> Hi Cheng,
>
> On Fri, 6 Mar 2020 17:35:06 +0800
> Cheng Jian <cj.chengjian@huawei.com> wrote:
>
>> Our system encountered a use-after-free when re-register a
>> same kretprobe. it access the hlist node in rp->free_instances
>> which has been released already.
>>
>> Prevent re-registration has been implemented for kprobe before,
>> but it's too late for kretprobe. We must check the re-registration
>> before re-initializing the kretprobe, otherwise it will destroy the
>> data and struct of the kretprobe registered, it can lead to memory
>> leak and use-after-free.
> I couldn't get how it cause use-after-free, but it causes memory leak.
> Anyway, if we can help to find a wrong usage, it might be good.
>
> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> BTW, I think we should use WARN_ON() for this error, because this
> means the caller is completely buggy.
>
> Thank you,

Hi Masami

When we try to re-register the same kretprobe, the register_kprobe()
return failed and try to free_rp_inst

    register_kretprobe()

        raw_spin_lock_init(&rp->lock);
        INIT_HLIST_HEAD(&rp->free_instances);    # re-init

        inst = kmalloc(sizeof(struct kretprobe_instance) +
p->data_size, GFP_KERNEL); # re-alloc

        ret = register_kprobe(&rp->kp);  # failed

        free_rp_inst(rp);   # free all the free_instances

at the same time, the kretprobe registed handle(trigger), it tries to
access the free_instances.

Since we broke the rp->lock and free_instances when re-registering, we
are accessing the newly

allocated free_instances and it's being released.

pre_handler_kretprobe

    ri = hlist_entry(rp->free_instances.first, struct
kretprobe_instance, hlist); # access the new free_instances. BOOM!!!

    hlist_del(&ri->hlist); #BOOM!!!


And the problem here is destructive, it destroyed all the data of the
previously registered kretprobe,
it can lead to a system crash, memory leak, use-after-free and even some
other unexpected behavior.

We have a testcase for it, and I put it in the attachment.


test on ARM64 QEMU

use-after-free call trace:

[ 39.852002] BUG: KASAN: use-after-free in
pre_handler_kretprobe+0x678/0x6b8 [107/7017]
[ 39.852460] Read of size 8 at addr ffff00002fb35408 by task
DTS202001190821/251
[ 39.852801]
[ 39.854101] CPU: 6 PID: 251 Comm: DTS202001190821 Tainted: G OE
5.6.0-rc4+ #8
[ 39.854610] Hardware name: linux,dummy-virt (DT)
[ 39.855316] Call trace:
[ 39.855520] dump_backtrace+0x0/0x390
[ 39.855758] show_stack+0x24/0x30
[ 39.855969] dump_stack+0x118/0x170
[ 39.856179] print_address_description.isra.10+0x74/0x3c0
[ 39.856451] __kasan_report+0x128/0x1d8
[ 39.856660] kasan_report+0xc/0x18
[ 39.856858] __asan_report_load8_noabort+0x18/0x20
[ 39.857132] pre_handler_kretprobe+0x678/0x6b8
[ 39.857377] kprobe_breakpoint_handler+0x108/0x580
[ 39.857622] call_break_hook+0x10c/0x1a0
[ 39.858201] brk_handler+0x28/0x88
[ 39.858503] do_debug_exception+0x138/0x2a8
[ 39.858723] el1_dbg+0x24/0x88
[ 39.858907] el1_sync_handler+0xb4/0x178
[ 39.859120] el1_sync+0x7c/0x100
[ 39.859309] _do_fork+0x0/0x8f8
[ 39.859494] el0_svc_common.constprop.2+0x11c/0x428
[ 39.859735] do_el0_svc+0x4c/0xe8
[ 39.859924] el0_svc+0x20/0x78
[ 39.860109] el0_sync_handler+0x104/0x380
[ 39.860322] el0_sync+0x140/0x180
[ 39.860644]
[ 39.860895] Allocated by task 399:
[ 39.861245] save_stack+0x28/0xc8
[ 39.861474] __kasan_kmalloc.isra.10+0xbc/0xd8
[ 39.861709] kasan_kmalloc+0xc/0x18
[ 39.862371] __kmalloc+0x128/0x2a8
[ 39.862561] register_kretprobe+0x1b0/0x868
[ 39.863834] kretprobe_init+0x8c/0x1000 [testKretprobe_007_1]
[ 39.864215] do_one_initcall+0xbc/0x4b0
[ 39.864471] do_init_module+0x194/0x580
[ 39.864730] load_module+0x4110/0x5870
[ 39.864966] __do_sys_init_module+0x264/0x390
[ 39.865268] __arm64_sys_init_module+0x70/0xa0
[ 39.865541] el0_svc_common.constprop.2+0x11c/0x428
[ 39.866287] do_el0_svc+0x4c/0xe8
[ 39.866522] el0_svc+0x20/0x78
[ 39.866746] el0_sync_handler+0x104/0x380
[ 39.867013] el0_sync+0x140/0x180
[ 39.867325]
[ 39.867486] Freed by task 399:
[ 39.867713] save_stack+0x28/0xc8
[ 39.867948] __kasan_slab_free+0x118/0x180
[ 39.868216] kasan_slab_free+0x10/0x18
[ 39.868470] kfree+0x1a0/0x2e0
[ 39.868691] register_kretprobe+0x598/0x868
[ 39.868986] kretprobe_init+0x8c/0x1000 [testKretprobe_007_1]
[ 39.869370] do_one_initcall+0xbc/0x4b0
[ 39.869637] do_init_module+0x194/0x580
[ 39.870332] load_module+0x4110/0x5870
[ 39.870590] __do_sys_init_module+0x264/0x390
[ 39.870877] __arm64_sys_init_module+0x70/0xa0
[ 39.871168] el0_svc_common.constprop.2+0x11c/0x428
[ 39.871471] do_el0_svc+0x4c/0xe8
[ 39.871705] el0_svc+0x20/0x78
[ 39.871925] el0_sync_handler+0x104/0x380
[ 39.872194] el0_sync+0x140/0x180
[ 39.872421]
[ 39.872592] The buggy address belongs to the object at ffff00002fb35400
[ 39.872592] which belongs to the cache kmalloc-128 of size 128
[ 39.873369] The buggy address is located 8 bytes inside of
[ 39.873369] 128-byte region [ffff00002fb35400, ffff00002fb35480)
[ 39.874572] The buggy address belongs to the page:
[ 39.875295] page:fffffe00009ecd00 refcount:1 mapcount:0
mapping:ffff00003200fc00 index:0x0 compound_mapcount: 0
[ 39.876782] flags: 0x7fffe0000010200(slab|head)
[ 39.877561] raw: 07fffe0000010200 dead000000000100 dead000000000122
ffff00003200fc00
[ 39.878554] raw: 0000000000000000 0000000000200020 00000001ffffffff
0000000000000000
[ 39.879064] page dumped because: kasan: bad access detected
[ 39.879493]
[ 39.879669] Memory state around the buggy address:
[ 39.880300] ffff00002fb35300: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
fc fc
[ 39.880772] ffff00002fb35380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc
fc fc
[ 39.881249] >ffff00002fb35400: fb fb fb fb fb fb fb fb fb fb fb fb fb
fb fb fb [29/7017]
[ 39.881738]
[ 39.882415] ffff00002fb35480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc
fc fc
[ 39.882836] ffff00002fb35500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb
fb fb
[ 39.883300]
==================================================================
[ 39.883761] Disabling lock debugging due to kernel taint



also with Oops

[ 39.884522] Unable to handle kernel paging request at virtual address
fbd5400000000024
[ 39.885133] Mem abort info:
[ 39.885377] ESR = 0x96000004
[ 39.886105] EC = 0x25: DABT (current EL), IL = 32 bits
[ 39.886507] SET = 0, FnV = 0
[ 39.886725] EA = 0, S1PTW = 0
[ 39.886950] Data abort info:
[ 39.887180] ISV = 0, ISS = 0x00000004
[ 39.887430] CM = 0, WnR = 0
[ 39.887755] [fbd5400000000024] address between user and kernel address
ranges
[ 39.888991] Internal error: Oops: 96000004 [#1] SMP
[ 39.890666] Dumping ftrace buffer:
[ 39.892131] (ftrace buffer empty)
[ 39.892724] Modules linked in: testKretprobe_007_1(OE+)
[ 39.893690] CPU: 6 PID: 251 Comm: DTS202001190821 Tainted: G B OE
5.6.0-rc4+ #8
[ 39.894802] Hardware name: linux,dummy-virt (DT)
[ 39.895197] pstate: 600003c5 (nZCv DAIF -PAN -UAO)
[ 39.895558] pc : pre_handler_kretprobe+0x130/0x6b8
[ 39.895880] lr : pre_handler_kretprobe+0x678/0x6b8
[ 39.896181] sp : ffff00002feef9b0
[ 39.896439] x29: ffff00002feef9b0 x28: 1fffe00005f66a81
[ 39.896845] x27: ffff00002fb34900 x26: 1fffe00005f66a80
[ 39.897214] x25: ffffa0000a442728 x24: 00000000000003
[ 39.897555] x23: ffff00002feefbd0 x22: ffff00002fb35408
[ 39.898279] x21: ffffa0000a442730 x20: ffff00002fb35400
[ 39.898619] x19: ffffa0000a442680 x18: 0000000000000000
[ 39.898955] x17: 0000000000000000 x16: 0000000000000000
[ 39.899290] x15: 0000000000000007 x14: 0000000000000003
[ 39.899624] x13: 0000000000000000 x12: 1ffff4000283803c
[ 39.899961] x11: ffff94000283803c x10: dfffa00000000000
[ 39.900362] x9 : ffff94000283803d x8 : 0000000000000001
[ 39.900700] x7 : ffffa000141c01e7 x6 : ffff94000283803d
[ 39.901032] x5 : ffff94000283803d x4 : ffff94000283803d
[ 39.901389] x3 : ffffa0001016bc3c x2 : 1bd5a00000000024
[ 39.901725] x1 : dead000000000122 x0 : dfffa00000000000
[ 39.902600] Call trace:
[ 39.902864] pre_handler_kretprobe+0x130/0x6b8
[ 39.903177] kprobe_breakpoint_handler+0x108/0x580
[ 39.903492] call_break_hook+0x10c/0x1a0
[ 39.903757] brk_handler+0x28/0x88
[ 39.904004] do_debug_exception+0x138/0x2a8
[ 39.904274] el1_dbg+0x24/0x88
[ 39.904494] el1_sync_handler+0xb4/0x178
[ 39.904756] el1_sync+0x7c/0x100
[ 39.904984] _do_fork+0x0/0x8f8
[ 39.905235] el0_svc_common.constprop.2+0x11c/0x428
[ 39.905553] do_el0_svc+0x4c/0xe8
[ 39.906016] el0_svc+0x20/0x78
[ 39.906435] el0_sync_handler+0x104/0x380
[ 39.906707] el0_sync+0x140/0x180
[ 39.907140] Code: f9400681 d2d40000 f2fbffe0 d343fc22 (38e06840)
[ 39.909096] ---[ end trace 9df6bc2e51e22a6c ]---
[ 39.910142] Kernel panic - not syncing: Fatal exception
[ 39.910992] SMP: stopping secondary CPUs
[ 39.912097] Dumping ftrace buffer:
[ 39.912348] (ftrace buffer empty)
[ 39.912722] Kernel Offset: disabled
[ 39.913317] CPU features: 0x10002,20006000
[ 39.913630] Memory Limit: none
[ 39.914612] ---[ end Kernel panic - not syncing: Fatal exception ]---


Thanks

----Cheng Jian

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