• Zhihao Cheng's avatar
    ubifs: ubifs_tnc_start_commit: Fix OOB in layout_in_gaps · 6abf5726
    Zhihao Cheng authored
    Running stress-test test_2 in mtd-utils on ubi device, sometimes we can
    get following oops message:
    
      BUG: unable to handle page fault for address: ffffffff00000140
      #PF: supervisor read access in kernel mode
      #PF: error_code(0x0000) - not-present page
      PGD 280a067 P4D 280a067 PUD 0
      Oops: 0000 [#1] SMP
      CPU: 0 PID: 60 Comm: kworker/u16:1 Kdump: loaded Not tainted 5.2.0 #13
      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0
      -0-ga698c8995f-prebuilt.qemu.org 04/01/2014
      Workqueue: writeback wb_workfn (flush-ubifs_0_0)
      RIP: 0010:rb_next_postorder+0x2e/0xb0
      Code: 80 db 03 01 48 85 ff 0f 84 97 00 00 00 48 8b 17 48 83 05 bc 80 db
      03 01 48 83 e2 fc 0f 84 82 00 00 00 48 83 05 b2 80 db 03 01 <48> 3b 7a
      10 48 89 d0 74 02 f3 c3 48 8b 52 08 48 83 05 a3 80 db 03
      RSP: 0018:ffffc90000887758 EFLAGS: 00010202
      RAX: ffff888129ae4700 RBX: ffff888138b08400 RCX: 0000000080800001
      RDX: ffffffff00000130 RSI: 0000000080800024 RDI: ffff888138b08400
      RBP: ffff888138b08400 R08: ffffea0004a6b920 R09: 0000000000000000
      R10: ffffc90000887740 R11: 0000000000000001 R12: ffff888128d48000
      R13: 0000000000000800 R14: 000000000000011e R15: 00000000000007c8
      FS:  0000000000000000(0000) GS:ffff88813ba00000(0000)
      knlGS:0000000000000000
      CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      CR2: ffffffff00000140 CR3: 000000013789d000 CR4: 00000000000006f0
      DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
      DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
      Call Trace:
        destroy_old_idx+0x5d/0xa0 [ubifs]
        ubifs_tnc_start_commit+0x4fe/0x1380 [ubifs]
        do_commit+0x3eb/0x830 [ubifs]
        ubifs_run_commit+0xdc/0x1c0 [ubifs]
    
    Above Oops are due to the slab-out-of-bounds happened in do-while of
    function layout_in_gaps indirectly called by ubifs_tnc_start_commit. In
    function layout_in_gaps, there is a do-while loop placing index nodes
    into the gaps created by obsolete index nodes in non-empty index LEBs
    until rest index nodes can totally be placed into pre-allocated empty
    LEBs. @c->gap_lebs points to a memory area(integer array) which records
    LEB numbers used by 'in-the-gaps' method. Whenever a fitable index LEB
    is found, corresponding lnum will be incrementally written into the
    memory area pointed by @c->gap_lebs. The size
    ((@c->lst.idx_lebs + 1) * sizeof(int)) of memory area is allocated before
    do-while loop and can not be changed in the loop. But @c->lst.idx_lebs
    could be increased by function ubifs_change_lp (called by
    layout_leb_in_gaps->ubifs_find_dirty_idx_leb->get_idx_gc_leb) during the
    loop. So, sometimes oob happens when number of cycles in do-while loop
    exceeds the original value of @c->lst.idx_lebs. See detail in
    https://bugzilla.kernel.org/show_bug.cgi?id=204229.
    This patch fixes oob in layout_in_gaps.
    Signed-off-by: default avatarZhihao Cheng <chengzhihao1@huawei.com>
    Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
    6abf5726
tnc_commit.c 27.7 KB