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    Subject[PATCH 3.16 013/114] assoc_array: don't call compare_object() on a node
    3.16.36-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jerome Marchand <jmarchan@redhat.com>

    commit 8d4a2ec1e0b41b0cf9a0c5cd4511da7f8e4f3de2 upstream.

    Changes since V1: fixed the description and added KASan warning.

    In assoc_array_insert_into_terminal_node(), we call the
    compare_object() method on all non-empty slots, even when they're
    not leaves, passing a pointer to an unexpected structure to
    compare_object(). Currently it causes an out-of-bound read access
    in keyring_compare_object detected by KASan (see below). The issue
    is easily reproduced with keyutils testsuite.
    Only call compare_object() when the slot is a leave.

    KASan warning:
    ==================================================================
    BUG: KASAN: slab-out-of-bounds in keyring_compare_object+0x213/0x240 at addr ffff880060a6f838
    Read of size 8 by task keyctl/1655
    =============================================================================
    BUG kmalloc-192 (Not tainted): kasan: bad access detected
    -----------------------------------------------------------------------------

    Disabling lock debugging due to kernel taint
    INFO: Allocated in assoc_array_insert+0xfd0/0x3a60 age=69 cpu=1 pid=1647
    ___slab_alloc+0x563/0x5c0
    __slab_alloc+0x51/0x90
    kmem_cache_alloc_trace+0x263/0x300
    assoc_array_insert+0xfd0/0x3a60
    __key_link_begin+0xfc/0x270
    key_create_or_update+0x459/0xaf0
    SyS_add_key+0x1ba/0x350
    entry_SYSCALL_64_fastpath+0x12/0x76
    INFO: Slab 0xffffea0001829b80 objects=16 used=8 fp=0xffff880060a6f550 flags=0x3fff8000004080
    INFO: Object 0xffff880060a6f740 @offset=5952 fp=0xffff880060a6e5d1

    Bytes b4 ffff880060a6f730: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f740: d1 e5 a6 60 00 88 ff ff 0e 00 00 00 00 00 00 00 ...`............
    Object ffff880060a6f750: 02 cf 8e 60 00 88 ff ff 02 c0 8e 60 00 88 ff ff ...`.......`....
    Object ffff880060a6f760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f770: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f790: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f7a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f7b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f7c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f7d0: 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f7e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    Object ffff880060a6f7f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
    CPU: 0 PID: 1655 Comm: keyctl Tainted: G B 4.5.0-rc4-kasan+ #291
    Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
    0000000000000000 000000001b2800b4 ffff880060a179e0 ffffffff81b60491
    ffff88006c802900 ffff880060a6f740 ffff880060a17a10 ffffffff815e2969
    ffff88006c802900 ffffea0001829b80 ffff880060a6f740 ffff880060a6e650
    Call Trace:
    [<ffffffff81b60491>] dump_stack+0x85/0xc4
    [<ffffffff815e2969>] print_trailer+0xf9/0x150
    [<ffffffff815e9454>] object_err+0x34/0x40
    [<ffffffff815ebe50>] kasan_report_error+0x230/0x550
    [<ffffffff819949be>] ? keyring_get_key_chunk+0x13e/0x210
    [<ffffffff815ec62d>] __asan_report_load_n_noabort+0x5d/0x70
    [<ffffffff81994cc3>] ? keyring_compare_object+0x213/0x240
    [<ffffffff81994cc3>] keyring_compare_object+0x213/0x240
    [<ffffffff81bc238c>] assoc_array_insert+0x86c/0x3a60
    [<ffffffff81bc1b20>] ? assoc_array_cancel_edit+0x70/0x70
    [<ffffffff8199797d>] ? __key_link_begin+0x20d/0x270
    [<ffffffff8199786c>] __key_link_begin+0xfc/0x270
    [<ffffffff81993389>] key_create_or_update+0x459/0xaf0
    [<ffffffff8128ce0d>] ? trace_hardirqs_on+0xd/0x10
    [<ffffffff81992f30>] ? key_type_lookup+0xc0/0xc0
    [<ffffffff8199e19d>] ? lookup_user_key+0x13d/0xcd0
    [<ffffffff81534763>] ? memdup_user+0x53/0x80
    [<ffffffff819983ea>] SyS_add_key+0x1ba/0x350
    [<ffffffff81998230>] ? key_get_type_from_user.constprop.6+0xa0/0xa0
    [<ffffffff828bcf4e>] ? retint_user+0x18/0x23
    [<ffffffff8128cc7e>] ? trace_hardirqs_on_caller+0x3fe/0x580
    [<ffffffff81004017>] ? trace_hardirqs_on_thunk+0x17/0x19
    [<ffffffff828bc432>] entry_SYSCALL_64_fastpath+0x12/0x76
    Memory state around the buggy address:
    ffff880060a6f700: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
    ffff880060a6f780: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
    >ffff880060a6f800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    ^
    ffff880060a6f880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    ffff880060a6f900: fc fc fc fc fc fc 00 00 00 00 00 00 00 00 00 00
    ==================================================================

    Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    lib/assoc_array.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/lib/assoc_array.c
    +++ b/lib/assoc_array.c
    @@ -523,7 +523,9 @@ static bool assoc_array_insert_into_term
    free_slot = i;
    continue;
    }
    - if (ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) {
    + if (assoc_array_ptr_is_leaf(ptr) &&
    + ops->compare_object(assoc_array_ptr_to_leaf(ptr),
    + index_key)) {
    pr_devel("replace in slot %d\n", i);
    edit->leaf_p = &node->slots[i];
    edit->dead_leaf = node->slots[i];
    \
     
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