• Dan Williams's avatar
    acpi, nfit, libnvdimm: fix / harden ars_status output length handling · efda1b5d
    Dan Williams authored
    Given ambiguities in the ACPI 6.1 definition of the "Output (Size)"
    field of the ARS (Address Range Scrub) Status command, a firmware
    implementation may in practice return 0, 4, or 8 to indicate that there
    is no output payload to process.
    
    The specification states "Size of Output Buffer in bytes, including this
    field.". However, 'Output Buffer' is also the name of the entire
    payload, and earlier in the specification it states "Max Query ARS
    Status Output Buffer Size: Maximum size of buffer (including the Status
    and Extended Status fields)".
    
    Without this fix if the BIOS happens to return 0 it causes memory
    corruption as evidenced by this result from the acpi_nfit_ctl() unit
    test.
    
     ars_status00000000: 00020000 00000000                    ........
     BUG: stack guard page was hit at ffffc90001750000 (stack is ffffc9000174c000..ffffc9000174ffff)
     kernel stack overflow (page fault): 0000 [#1] SMP DEBUG_PAGEALLOC
     task: ffff8803332d2ec0 task.stack: ffffc9000174c000
     RIP: 0010:[<ffffffff814cfe72>]  [<ffffffff814cfe72>] __memcpy+0x12/0x20
     RSP: 0018:ffffc9000174f9a8  EFLAGS: 00010246
     RAX: ffffc9000174fab8 RBX: 0000000000000000 RCX: 000000001fffff56
     RDX: 0000000000000000 RSI: ffff8803231f5a08 RDI: ffffc90001750000
     RBP: ffffc9000174fa88 R08: ffffc9000174fab0 R09: ffff8803231f54b8
     R10: 0000000000000008 R11: 0000000000000001 R12: 0000000000000000
     R13: 0000000000000000 R14: 0000000000000003 R15: ffff8803231f54a0
     FS:  00007f3a611af640(0000) GS:ffff88033ed00000(0000) knlGS:0000000000000000
     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
     CR2: ffffc90001750000 CR3: 0000000325b20000 CR4: 00000000000406e0
     Stack:
      ffffffffa00bc60d 0000000000000008 ffffc90000000001 ffffc9000174faac
      0000000000000292 ffffffffa00c24e4 ffffffffa00c2914 0000000000000000
      0000000000000000 ffffffff00000003 ffff880331ae8ad0 0000000800000246
     Call Trace:
      [<ffffffffa00bc60d>] ? acpi_nfit_ctl+0x49d/0x750 [nfit]
      [<ffffffffa01f4fe0>] nfit_test_probe+0x670/0xb1b [nfit_test]
    
    Cc: <stable@vger.kernel.org>
    Fixes: 747ffe11 ("libnvdimm, tools/testing/nvdimm: fix 'ars_status' output buffer sizing")
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    efda1b5d
core.c 77.8 KB