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    Subject[PATCH 4.9 05/77] mbcache: initialize entry->e_referenced in mb_cache_entry_create()
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Alexander Potapenko <glider@google.com>

    commit 3876bbe27d04b848750d5310a37d6b76b593f648 upstream.

    KMSAN reported use of uninitialized |entry->e_referenced| in a condition
    in mb_cache_shrink():

    ==================================================================
    BUG: KMSAN: use of uninitialized memory in mb_cache_shrink+0x3b4/0xc50 fs/mbcache.c:287
    CPU: 2 PID: 816 Comm: kswapd1 Not tainted 4.11.0-rc5+ #2877
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
    01/01/2011
    Call Trace:
    __dump_stack lib/dump_stack.c:16 [inline]
    dump_stack+0x172/0x1c0 lib/dump_stack.c:52
    kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:927
    __msan_warning_32+0x61/0xb0 mm/kmsan/kmsan_instr.c:469
    mb_cache_shrink+0x3b4/0xc50 fs/mbcache.c:287
    mb_cache_scan+0x67/0x80 fs/mbcache.c:321
    do_shrink_slab mm/vmscan.c:397 [inline]
    shrink_slab+0xc3d/0x12d0 mm/vmscan.c:500
    shrink_node+0x208f/0x2fd0 mm/vmscan.c:2603
    kswapd_shrink_node mm/vmscan.c:3172 [inline]
    balance_pgdat mm/vmscan.c:3289 [inline]
    kswapd+0x160f/0x2850 mm/vmscan.c:3478
    kthread+0x46c/0x5f0 kernel/kthread.c:230
    ret_from_fork+0x29/0x40 arch/x86/entry/entry_64.S:430
    chained origin:
    save_stack_trace+0x37/0x40 arch/x86/kernel/stacktrace.c:59
    kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302 [inline]
    kmsan_save_stack mm/kmsan/kmsan.c:317 [inline]
    kmsan_internal_chain_origin+0x12a/0x1f0 mm/kmsan/kmsan.c:547
    __msan_store_shadow_origin_1+0xac/0x110 mm/kmsan/kmsan_instr.c:257
    mb_cache_entry_create+0x3b3/0xc60 fs/mbcache.c:95
    ext4_xattr_cache_insert fs/ext4/xattr.c:1647 [inline]
    ext4_xattr_block_set+0x4c82/0x5530 fs/ext4/xattr.c:1022
    ext4_xattr_set_handle+0x1332/0x20a0 fs/ext4/xattr.c:1252
    ext4_xattr_set+0x4d2/0x680 fs/ext4/xattr.c:1306
    ext4_xattr_trusted_set+0x8d/0xa0 fs/ext4/xattr_trusted.c:36
    __vfs_setxattr+0x703/0x790 fs/xattr.c:149
    __vfs_setxattr_noperm+0x27a/0x6f0 fs/xattr.c:180
    vfs_setxattr fs/xattr.c:223 [inline]
    setxattr+0x6ae/0x790 fs/xattr.c:449
    path_setxattr+0x1eb/0x380 fs/xattr.c:468
    SYSC_lsetxattr+0x8d/0xb0 fs/xattr.c:490
    SyS_lsetxattr+0x77/0xa0 fs/xattr.c:486
    entry_SYSCALL_64_fastpath+0x13/0x94
    origin:
    save_stack_trace+0x37/0x40 arch/x86/kernel/stacktrace.c:59
    kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302 [inline]
    kmsan_internal_poison_shadow+0xb1/0x1a0 mm/kmsan/kmsan.c:198
    kmsan_kmalloc+0x7f/0xe0 mm/kmsan/kmsan.c:337
    kmem_cache_alloc+0x1c2/0x1e0 mm/slub.c:2766
    mb_cache_entry_create+0x283/0xc60 fs/mbcache.c:86
    ext4_xattr_cache_insert fs/ext4/xattr.c:1647 [inline]
    ext4_xattr_block_set+0x4c82/0x5530 fs/ext4/xattr.c:1022
    ext4_xattr_set_handle+0x1332/0x20a0 fs/ext4/xattr.c:1252
    ext4_xattr_set+0x4d2/0x680 fs/ext4/xattr.c:1306
    ext4_xattr_trusted_set+0x8d/0xa0 fs/ext4/xattr_trusted.c:36
    __vfs_setxattr+0x703/0x790 fs/xattr.c:149
    __vfs_setxattr_noperm+0x27a/0x6f0 fs/xattr.c:180
    vfs_setxattr fs/xattr.c:223 [inline]
    setxattr+0x6ae/0x790 fs/xattr.c:449
    path_setxattr+0x1eb/0x380 fs/xattr.c:468
    SYSC_lsetxattr+0x8d/0xb0 fs/xattr.c:490
    SyS_lsetxattr+0x77/0xa0 fs/xattr.c:486
    entry_SYSCALL_64_fastpath+0x13/0x94
    ==================================================================

    Signed-off-by: Alexander Potapenko <glider@google.com>
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Cc: stable@vger.kernel.org # v4.6
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/mbcache.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/fs/mbcache.c
    +++ b/fs/mbcache.c
    @@ -93,6 +93,7 @@ int mb_cache_entry_create(struct mb_cach
    entry->e_key = key;
    entry->e_block = block;
    entry->e_reusable = reusable;
    + entry->e_referenced = 0;
    head = mb_cache_entry_head(cache, key);
    hlist_bl_lock(head);
    hlist_bl_for_each_entry(dup, dup_node, head, e_hash_list) {

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