lkml.org 
[lkml]   [2017]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.18 30/45] powerpc/eeh: Avoid use after free in eeh_handle_special_event()
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

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

    From: Russell Currey <ruscur@russell.cc>

    commit daeba2956f32f91f3493788ff6ee02fb1b2f02fa upstream.

    eeh_handle_special_event() is called when an EEH event is detected but
    can't be narrowed down to a specific PE. This function looks through
    every PE to find one in an erroneous state, then calls the regular event
    handler eeh_handle_normal_event() once it knows which PE has an error.

    However, if eeh_handle_normal_event() found that the PE cannot possibly
    be recovered, it will free it, rendering the passed PE stale.
    This leads to a use after free in eeh_handle_special_event() as it attempts to
    clear the "recovering" state on the PE after eeh_handle_normal_event() returns.

    Thus, make sure the PE is valid when attempting to clear state in
    eeh_handle_special_event().

    Fixes: 8a6b1bc70dbb ("powerpc/eeh: EEH core to handle special event")
    Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
    Signed-off-by: Russell Currey <ruscur@russell.cc>
    Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


    ---
    arch/powerpc/kernel/eeh_driver.c | 19 +++++++++++++++----
    1 file changed, 15 insertions(+), 4 deletions(-)

    --- a/arch/powerpc/kernel/eeh_driver.c
    +++ b/arch/powerpc/kernel/eeh_driver.c
    @@ -678,7 +678,7 @@ static int eeh_reset_device(struct eeh_p
    */
    #define MAX_WAIT_FOR_RECOVERY 300

    -static void eeh_handle_normal_event(struct eeh_pe *pe)
    +static bool eeh_handle_normal_event(struct eeh_pe *pe)
    {
    struct pci_bus *frozen_bus;
    int rc = 0;
    @@ -688,7 +688,7 @@ static void eeh_handle_normal_event(stru
    if (!frozen_bus) {
    pr_err("%s: Cannot find PCI bus for PHB#%d-PE#%x\n",
    __func__, pe->phb->global_number, pe->addr);
    - return;
    + return false;
    }

    eeh_pe_update_time_stamp(pe);
    @@ -805,7 +805,7 @@ static void eeh_handle_normal_event(stru
    pr_info("EEH: Notify device driver to resume\n");
    eeh_pe_dev_traverse(pe, eeh_report_resume, NULL);

    - return;
    + return false;

    excess_failures:
    /*
    @@ -845,7 +845,11 @@ perm_error:
    pci_lock_rescan_remove();
    pcibios_remove_pci_devices(frozen_bus);
    pci_unlock_rescan_remove();
    +
    + /* The passed PE should no longer be used */
    + return true;
    }
    + return false;
    }

    static void eeh_handle_special_event(void)
    @@ -911,7 +915,14 @@ static void eeh_handle_special_event(voi
    */
    if (rc == EEH_NEXT_ERR_FROZEN_PE ||
    rc == EEH_NEXT_ERR_FENCED_PHB) {
    - eeh_handle_normal_event(pe);
    + /*
    + * eeh_handle_normal_event() can make the PE stale if it
    + * determines that the PE cannot possibly be recovered.
    + * Don't modify the PE state if that's the case.
    + */
    + if (eeh_handle_normal_event(pe))
    + continue;
    +
    eeh_pe_state_clear(pe, EEH_PE_RECOVERING);
    } else {
    pci_lock_rescan_remove();

    \
     
     \ /
      Last update: 2017-06-12 17:48    [W:4.304 / U:0.336 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site