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    Subject[PATCH 4.9 040/152] powerpc/crypto/crc32c-vpmsum: Fix missing preempt_disable()
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Michael Ellerman <mpe@ellerman.id.au>

    commit 4749228f022893faf54a3dbc70796f78b7d4f342 upstream.

    In crc32c_vpmsum() we call enable_kernel_altivec() without first
    disabling preemption, which is not allowed:

    WARNING: CPU: 9 PID: 2949 at ../arch/powerpc/kernel/process.c:277 enable_kernel_altivec+0x100/0x120
    Modules linked in: dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio libcrc32c vmx_crypto ...
    CPU: 9 PID: 2949 Comm: docker Not tainted 4.11.0-rc5-compiler_gcc-6.3.1-00033-g308ac7563944 #381
    ...
    NIP [c00000000001e320] enable_kernel_altivec+0x100/0x120
    LR [d000000003df0910] crc32c_vpmsum+0x108/0x150 [crc32c_vpmsum]
    Call Trace:
    0xc138fd09 (unreliable)
    crc32c_vpmsum+0x108/0x150 [crc32c_vpmsum]
    crc32c_vpmsum_update+0x3c/0x60 [crc32c_vpmsum]
    crypto_shash_update+0x88/0x1c0
    crc32c+0x64/0x90 [libcrc32c]
    dm_bm_checksum+0x48/0x80 [dm_persistent_data]
    sb_check+0x84/0x120 [dm_thin_pool]
    dm_bm_validate_buffer.isra.0+0xc0/0x1b0 [dm_persistent_data]
    dm_bm_read_lock+0x80/0xf0 [dm_persistent_data]
    __create_persistent_data_objects+0x16c/0x810 [dm_thin_pool]
    dm_pool_metadata_open+0xb0/0x1a0 [dm_thin_pool]
    pool_ctr+0x4cc/0xb60 [dm_thin_pool]
    dm_table_add_target+0x16c/0x3c0
    table_load+0x184/0x400
    ctl_ioctl+0x2f0/0x560
    dm_ctl_ioctl+0x38/0x50
    do_vfs_ioctl+0xd8/0x920
    SyS_ioctl+0x68/0xc0
    system_call+0x38/0xfc

    It used to be sufficient just to call pagefault_disable(), because that
    also disabled preemption. But the two were decoupled in commit 8222dbe21e79
    ("sched/preempt, mm/fault: Decouple preemption from the page fault
    logic") in mid 2015.

    So add the missing preempt_disable/enable(). We should also call
    disable_kernel_fp(), although it does nothing by default, there is a
    debug switch to make it active and all enables should be paired with
    disables.

    Fixes: 6dd7a82cc54e ("crypto: powerpc - Add POWER8 optimised crc32c")
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/powerpc/crypto/crc32c-vpmsum_glue.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/arch/powerpc/crypto/crc32c-vpmsum_glue.c
    +++ b/arch/powerpc/crypto/crc32c-vpmsum_glue.c
    @@ -33,10 +33,13 @@ static u32 crc32c_vpmsum(u32 crc, unsign
    }

    if (len & ~VMX_ALIGN_MASK) {
    + preempt_disable();
    pagefault_disable();
    enable_kernel_altivec();
    crc = __crc32c_vpmsum(crc, p, len & ~VMX_ALIGN_MASK);
    + disable_kernel_altivec();
    pagefault_enable();
    + preempt_enable();
    }

    tail = len & VMX_ALIGN_MASK;

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