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Date:   Sun, 13 May 2018 16:02:37 -0700
From:   Eric Biggers <ebiggers3@gmail.com>
To:     linux-rdma@vger.kernel.org, Doug Ledford <dledford@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>, rds-devel@oss.oracle.com
Cc:     syzbot <syzbot+db1c219466daac1083df@syzkaller.appspotmail.com>,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: KASAN: use-after-free Read in __list_add_valid (5)
Message-ID: <20180513230237.GG677@sol.localdomain>
References: <089e0825fc78410eaa056845781e@google.com>
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On Sun, Mar 25, 2018 at 05:01:03PM -0700, syzbot wrote:
> Hello,
> 
> syzbot hit the following crash on upstream commit
> bcfc1f4554662d8f2429ac8bd96064a59c149754 (Sat Mar 24 16:50:12 2018 +0000)
> Merge tag 'pinctrl-v4.16-3' of
> git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=db1c219466daac1083df
> 
> So far this crash happened 4 times on upstream.
> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5164223906709504
> syzkaller reproducer:
> https://syzkaller.appspot.com/x/repro.syz?id=5357898477600768
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5549124782915584
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=-5034017172441945317
> compiler: gcc (GCC) 7.1.1 20170620
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+db1c219466daac1083df@syzkaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
> 
> IPVS: ftp: loaded support on port[0] = 21
> IPVS: ftp: loaded support on port[0] = 21
> IPVS: ftp: loaded support on port[0] = 21
> ==================================================================
> BUG: KASAN: use-after-free in __list_add_valid+0xc6/0xd0 lib/list_debug.c:26
> IPVS: ftp: loaded support on port[0] = 21
> Read of size 8 at addr ffff8801ca8adcd8 by task syzkaller401155/4288
> 
> CPU: 0 PID: 4288 Comm: syzkaller401155 Not tainted 4.16.0-rc6+ #365
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x24d lib/dump_stack.c:53
>  print_address_description+0x73/0x250 mm/kasan/report.c:256
> IPVS: ftp: loaded support on port[0] = 21
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report+0x23c/0x360 mm/kasan/report.c:412
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>  __list_add_valid+0xc6/0xd0 lib/list_debug.c:26
>  __list_add include/linux/list.h:60 [inline]
>  list_add_tail include/linux/list.h:93 [inline]
>  cma_listen_on_all drivers/infiniband/core/cma.c:2309 [inline]
>  rdma_listen+0x581/0x8e0 drivers/infiniband/core/cma.c:3333
>  ucma_listen+0x172/0x1f0 drivers/infiniband/core/ucma.c:1074
>  ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1649
> IPVS: ftp: loaded support on port[0] = 21
>  __vfs_write+0xef/0x970 fs/read_write.c:480
> IPVS: ftp: loaded support on port[0] = 21
>  vfs_write+0x189/0x510 fs/read_write.c:544
>  SYSC_write fs/read_write.c:589 [inline]
>  SyS_write+0xef/0x220 fs/read_write.c:581
>  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
> IPVS: ftp: loaded support on port[0] = 21
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> RIP: 0033:0x44a9e9
> RSP: 002b:00007f94303f3da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00000000006e29fc RCX: 000000000044a9e9
> RDX: 0000000000000010 RSI: 0000000020000000 RDI: 0000000000000004
> RBP: 00000000006e29f8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 2f646e6162696e69
> R13: 666e692f7665642f R14: 7073642f7665642f R15: 0000000000000009
> 
> Allocated by task 4284:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
>  kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607
>  kmalloc include/linux/slab.h:512 [inline]
>  kzalloc include/linux/slab.h:701 [inline]
>  rdma_create_id+0xd0/0x630 drivers/infiniband/core/cma.c:787
>  ucma_create_id+0x35f/0x920 drivers/infiniband/core/ucma.c:480
>  ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1649
>  __vfs_write+0xef/0x970 fs/read_write.c:480
>  vfs_write+0x189/0x510 fs/read_write.c:544
>  SYSC_write fs/read_write.c:589 [inline]
>  SyS_write+0xef/0x220 fs/read_write.c:581
>  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> Freed by task 4284:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
>  __cache_free mm/slab.c:3485 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3800
>  rdma_destroy_id+0x821/0xda0 drivers/infiniband/core/cma.c:1691
>  ucma_close+0x100/0x2f0 drivers/infiniband/core/ucma.c:1728
>  __fput+0x327/0x7e0 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x199/0x270 kernel/task_work.c:113
>  exit_task_work include/linux/task_work.h:22 [inline]
>  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
>  do_group_exit+0x149/0x400 kernel/exit.c:968
>  get_signal+0x73a/0x16d0 kernel/signal.c:2469
>  do_signal+0x90/0x1e90 arch/x86/kernel/signal.c:809
>  exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> The buggy address belongs to the object at ffff8801ca8adb00
>  which belongs to the cache kmalloc-1024 of size 1024
> The buggy address is located 472 bytes inside of
>  1024-byte region [ffff8801ca8adb00, ffff8801ca8adf00)
> The buggy address belongs to the page:
> page:ffffea00072a2b00 count:1 mapcount:0 mapping:ffff8801ca8ac000 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
> raw: 02fffc0000008100 ffff8801ca8ac000 0000000000000000 0000000100000007
> raw: ffffea00072969a0 ffffea00072c5d20 ffff8801dac00ac0 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8801ca8adb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801ca8adc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8801ca8adc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                                     ^
>  ffff8801ca8add00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801ca8add80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> 
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@googlegroups.com.
> 
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
> #syz fix: exact-commit-title
> If you want to test a patch for this bug, please reply with:
> #syz test: git://repo/address.git branch
> and provide the patch inline or as an attachment.
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line in the email body.

Still reproducible on Linus' tree (commit 66e1c94db3cd4e) and on linux-next
(next-20180511).  Here's a simplified reproducer:

#include <fcntl.h>
#include <netinet/in.h>
#include <pthread.h>
#include <rdma/rdma_user_cm.h>
#include <unistd.h>

static int cmfd;
static volatile uint64_t id;

static void *thr1(void *_ignored)
{
        for (;;) {
                struct {
                        struct rdma_ucm_cmd_hdr hdr;
                        struct rdma_ucm_create_id create;
                } msg = {
                        .hdr = {
                                .cmd = RDMA_USER_CM_CMD_CREATE_ID,
                                .out = 8
                        },
                        .create = {
                                .response = (unsigned long)&id,
                                .ps = 2, /* RDMA_PS_IPOIB */
                        },
                };
                write(cmfd, &msg, sizeof(msg));
        }
}

static void *thr2(void *_ignored)
{
        for (;;) {
                struct {
                        struct rdma_ucm_cmd_hdr hdr;
                        struct rdma_ucm_bind_ip bind;
                } msg = {
                        .hdr = { .cmd = RDMA_USER_CM_CMD_BIND_IP },
                        .bind = {
                                .addr = {
                                        .sin6_family = AF_INET6,
                                        .sin6_addr = { .s6_addr = { 0xff } },
                                },
                                .id = id,
                        },
                };
                write(cmfd, &msg, sizeof(msg));
        }
}

static void *thr3(void *_ignored)
{
        for (;;) {
                struct {
                        struct rdma_ucm_cmd_hdr hdr;
                        struct rdma_ucm_listen listen;
                } msg = {
                        .hdr = { .cmd = RDMA_USER_CM_CMD_LISTEN },
                        .listen = { .id = id },
                };
                write(cmfd, &msg, sizeof(msg));
        }
}

int main()
{
        pthread_t t[3];

        cmfd = open("/dev/infiniband/rdma_cm", O_WRONLY);

        pthread_create(&t[0], NULL, thr1, NULL);
        pthread_create(&t[1], NULL, thr2, NULL);
        pthread_create(&t[2], NULL, thr3, NULL);
        usleep(100000);
}