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    SubjectRe: [PATCH] tpm: Fix NULL pointer dereference in tpm_transmit()
    On Wed, Jul 04, 2018 at 02:33:40PM +0530, Shirish S wrote:
    > During system shutdown,
    > tpm_class_shutdown() when called with TPM_CHIP_FLAG_TPM2
    > flag set, makes chip->ops NULL.
    >
    > However tpm_chip_unregister() called later in shutdown
    > sequence tries to access chip->ops in tpm_try_transmit()
    > leading the NULL pointer dereference.
    >
    > This patch fixes this issue.
    > Below is the trace for reference:
    >
    > BUG: unable to handle kernel NULL pointer dereference at
    > 0000000000000048
    > IP: tpm_transmit+0x267/0x565
    > PGD 0 P4D 0
    > Oops: 0000 [#1] PREEMPT SMP NOPTI
    > ...
    > task: ffff937c847fe580 task.stack: ffffa79f80b04000
    > RIP: 0010:tpm_transmit+0x267/0x565
    > RSP: 0018:ffffa79f80b07c08 EFLAGS: 00010286
    > RAX: 0000000000000000 RBX: ffff937ca9bc8000 RCX: ffff937c847fe580
    > RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffffffff98e3cd40
    > RBP: ffffa79f80b07c88 R08: 000000000001fff4 R09: 0000000000000000
    > R10: 0000000000000000 R11: 0000000000000000 R12: ffffa79f80b07cd4
    > R13: 000000000000008c R14: ffffffffffffffc3 R15: 0000000000000000
    > FS: 00007ef31f747740(0000) GS:ffff937caed00000(0000)
    > knlGS:0000000000000000
    > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    > CR2: 0000000000000048 CR3: 00000001243d2000 CR4: 00000000001406e0
    > Call Trace:
    > tpm_transmit_cmd+0x25/0x70
    > tpm2_shutdown+0x69/0xa3
    > ? __radix_tree_replace+0xd9/0x120
    > ? idr_replace_ext+0x92/0xb6
    > tpm_chip_unregister+0xaa/0xdb
    > cr50_i2c_shutdown+0x1e/0x41

    It makes no sense to call something like tpm_unregister from shutdown.

    Jason

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