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    Subject[PATCH 5.10 083/221] integrity: double check iint_cache was initialized
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    From: Mimi Zohar <zohar@linux.ibm.com>

    commit 92063f3ca73aab794bd5408d3361fd5b5ea33079 upstream.

    The kernel may be built with multiple LSMs, but only a subset may be
    enabled on the boot command line by specifying "lsm=". Not including
    "integrity" on the ordered LSM list may result in a NULL deref.

    As reported by Dmitry Vyukov:
    in qemu:
    qemu-system-x86_64 -enable-kvm -machine q35,nvdimm -cpu
    max,migratable=off -smp 4 -m 4G,slots=4,maxmem=16G -hda
    wheezy.img -kernel arch/x86/boot/bzImage -nographic -vga std
    -soundhw all -usb -usbdevice tablet -bt hci -bt device:keyboard
    -net user,host=10.0.2.10,hostfwd=tcp::10022-:22 -net
    nic,model=virtio-net-pci -object
    memory-backend-file,id=pmem1,share=off,mem-path=/dev/zero,size=64M
    -device nvdimm,id=nvdimm1,memdev=pmem1 -append "console=ttyS0
    root=/dev/sda earlyprintk=serial rodata=n oops=panic panic_on_warn=1
    panic=86400 lsm=smack numa=fake=2 nopcid dummy_hcd.num=8" -pidfile
    vm_pid -m 2G -cpu host

    But it crashes on NULL deref in integrity_inode_get during boot:

    Run /sbin/init as init process
    BUG: kernel NULL pointer dereference, address: 000000000000001c
    PGD 0 P4D 0
    Oops: 0000 [#1] PREEMPT SMP KASAN
    CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.12.0-rc2+ #97
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
    rel-1.13.0-44-g88ab0c15525c-prebuilt.qemu.org 04/01/2014
    RIP: 0010:kmem_cache_alloc+0x2b/0x370 mm/slub.c:2920
    Code: 57 41 56 41 55 41 54 41 89 f4 55 48 89 fd 53 48 83 ec 10 44 8b
    3d d9 1f 90 0b 65 48 8b 04 25 28 00 00 00 48 89 44 24 08 31 c0 <8b> 5f
    1c 4cf
    RSP: 0000:ffffc9000032f9d8 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: ffff888017fc4f00 RCX: 0000000000000000
    RDX: ffff888040220000 RSI: 0000000000000c40 RDI: 0000000000000000
    RBP: 0000000000000000 R08: 0000000000000000 R09: ffff888019263627
    R10: ffffffff83937cd1 R11: 0000000000000000 R12: 0000000000000c40
    R13: ffff888019263538 R14: 0000000000000000 R15: 0000000000ffffff
    FS: 0000000000000000(0000) GS:ffff88802d180000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 000000000000001c CR3: 000000000b48e000 CR4: 0000000000750ee0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    PKRU: 55555554
    Call Trace:
    integrity_inode_get+0x47/0x260 security/integrity/iint.c:105
    process_measurement+0x33d/0x17e0 security/integrity/ima/ima_main.c:237
    ima_bprm_check+0xde/0x210 security/integrity/ima/ima_main.c:474
    security_bprm_check+0x7d/0xa0 security/security.c:845
    search_binary_handler fs/exec.c:1708 [inline]
    exec_binprm fs/exec.c:1761 [inline]
    bprm_execve fs/exec.c:1830 [inline]
    bprm_execve+0x764/0x19a0 fs/exec.c:1792
    kernel_execve+0x370/0x460 fs/exec.c:1973
    try_to_run_init_process+0x14/0x4e init/main.c:1366
    kernel_init+0x11d/0x1b8 init/main.c:1477
    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
    Modules linked in:
    CR2: 000000000000001c
    ---[ end trace 22d601a500de7d79 ]---

    Since LSMs and IMA may be configured at build time, but not enabled at
    run time, panic the system if "integrity" was not initialized before use.

    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Fixes: 79f7865d844c ("LSM: Introduce "lsm=" for boottime LSM selection")
    Cc: stable@vger.kernel.org
    Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    security/integrity/iint.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- a/security/integrity/iint.c
    +++ b/security/integrity/iint.c
    @@ -98,6 +98,14 @@ struct integrity_iint_cache *integrity_i
    struct rb_node *node, *parent = NULL;
    struct integrity_iint_cache *iint, *test_iint;

    + /*
    + * The integrity's "iint_cache" is initialized at security_init(),
    + * unless it is not included in the ordered list of LSMs enabled
    + * on the boot command line.
    + */
    + if (!iint_cache)
    + panic("%s: lsm=integrity required.\n", __func__);
    +
    iint = integrity_iint_find(inode);
    if (iint)
    return iint;

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