linux-kernel - [syzbot] memory leak in prepare_kernel

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Date:   Mon, 20 Sep 2021 08:42:36 -0700
From:   syzbot <syzbot+b214edc6e43f8da65554@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, ebiederm@...ssion.com,
        legion@...nel.org, linux-kernel@...r.kernel.org,
        linux@...musvillemoes.dk, syzkaller-bugs@...glegroups.com,
        yangyingliang@...wei.com
Subject: [syzbot] memory leak in prepare_kernel_cred

Hello,

syzbot found the following issue on:

HEAD commit:    4357f03d6611 Merge tag 'pm-5.15-rc2' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16260b9b300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=84e947373389eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=b214edc6e43f8da65554
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17a7cb3b300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=103f8f2d300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b214edc6e43f8da65554@...kaller.appspotmail.com

write to /proc/sys/kernel/hung_task_check_interval_secs failed: No such file or directory
write to /proc/sys/kernel/softlockup_all_cpu_backtrace failed: No such file or directory
BUG: memory leak
unreferenced object 0xffff8881046d5480 (size 176):
  comm "kworker/u4:0", pid 6631, jiffies 4294994696 (age 35.750s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81275931>] prepare_kernel_cred+0x21/0x2e0 kernel/cred.c:724
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff888102054040 (size 32):
  comm "kworker/u4:0", pid 6631, jiffies 4294994696 (age 35.750s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 b0 12 05 40 81 88 ff ff  ...........@....
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff8213e79f>] lsm_cred_alloc security/security.c:537 [inline]
    [<ffffffff8213e79f>] security_prepare_creds+0x9f/0xc0 security/security.c:1691
    [<ffffffff81275ab5>] prepare_kernel_cred+0x1a5/0x2e0 kernel/cred.c:760
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff8881046d50c0 (size 176):
  comm "kworker/u4:0", pid 6633, jiffies 4294994696 (age 35.750s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81275931>] prepare_kernel_cred+0x21/0x2e0 kernel/cred.c:724
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff88810493f6c0 (size 176):
  comm "kworker/u4:0", pid 6634, jiffies 4294994696 (age 35.750s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81275931>] prepare_kernel_cred+0x21/0x2e0 kernel/cred.c:724
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff888104cec5e0 (size 32):
  comm "kworker/u4:0", pid 6634, jiffies 4294994696 (age 35.750s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 b0 12 05 40 81 88 ff ff  ...........@....
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff8213e79f>] lsm_cred_alloc security/security.c:537 [inline]
    [<ffffffff8213e79f>] security_prepare_creds+0x9f/0xc0 security/security.c:1691
    [<ffffffff81275ab5>] prepare_kernel_cred+0x1a5/0x2e0 kernel/cred.c:760
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff88810382b780 (size 176):
  comm "kworker/u4:0", pid 6637, jiffies 4294994700 (age 35.710s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81275931>] prepare_kernel_cred+0x21/0x2e0 kernel/cred.c:724
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff888102054060 (size 32):
  comm "kworker/u4:0", pid 6637, jiffies 4294994700 (age 35.710s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 b0 12 05 40 81 88 ff ff  ...........@....
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff8213e79f>] lsm_cred_alloc security/security.c:537 [inline]
    [<ffffffff8213e79f>] security_prepare_creds+0x9f/0xc0 security/security.c:1691
    [<ffffffff81275ab5>] prepare_kernel_cred+0x1a5/0x2e0 kernel/cred.c:760
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

BUG: memory leak
unreferenced object 0xffff888104c0a780 (size 176):
  comm "kworker/u4:0", pid 6630, jiffies 4294994702 (age 35.690s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81275931>] prepare_kernel_cred+0x21/0x2e0 kernel/cred.c:724
    [<ffffffff8125fc6d>] call_usermodehelper_exec_async+0x5d/0x1c0 kernel/umh.c:91
    [<ffffffff8100234f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295



---
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