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    Subject[PATCH 4.4 160/342] EDAC, mc_sysfs: Fix freeing bus name
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Borislav Petkov <bp@suse.de>

    commit 12e26969b32c79018165d52caff3762135614aa1 upstream.

    I get the splat below when modprobing/rmmoding EDAC drivers. It happens
    because bus->name is invalid after bus_unregister() has run. The Code: section
    below corresponds to:

    .loc 1 1108 0
    movq 672(%rbx), %rax # mci_1(D)->bus, mci_1(D)->bus
    .loc 1 1109 0
    popq %rbx #

    .loc 1 1108 0
    movq (%rax), %rdi # _7->name,
    jmp kfree #

    and %rax has some funky stuff 2030203020312030 which looks a lot like
    something walked over it.

    Fix that by saving the name ptr before doing stuff to string it points to.

    general protection fault: 0000 [#1] SMP
    Modules linked in: ...
    CPU: 4 PID: 10318 Comm: modprobe Tainted: G I EN 3.12.51-11-default+ #48
    Hardware name: HP ProLiant DL380 G7, BIOS P67 05/05/2011
    task: ffff880311320280 ti: ffff88030da3e000 task.ti: ffff88030da3e000
    RIP: 0010:[<ffffffffa019da92>] [<ffffffffa019da92>] edac_unregister_sysfs+0x22/0x30 [edac_core]
    RSP: 0018:ffff88030da3fe28 EFLAGS: 00010292
    RAX: 2030203020312030 RBX: ffff880311b4e000 RCX: 000000000000095c
    RDX: 0000000000000001 RSI: ffff880327bb9600 RDI: 0000000000000286
    RBP: ffff880311b4e750 R08: 0000000000000000 R09: ffffffff81296110
    R10: 0000000000000400 R11: 0000000000000000 R12: ffff88030ba1ac68
    R13: 0000000000000001 R14: 00000000011b02f0 R15: 0000000000000000
    FS: 00007fc9bf8f5700(0000) GS:ffff8801a7c40000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
    CR2: 0000000000403c90 CR3: 000000019ebdf000 CR4: 00000000000007e0
    Stack:
    Call Trace:
    i7core_unregister_mci.isra.9
    i7core_remove
    pci_device_remove
    __device_release_driver
    driver_detach
    bus_remove_driver
    pci_unregister_driver
    i7core_exit
    SyS_delete_module
    system_call_fastpath
    0x7fc9bf426536
    Code: 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90 53 48 89 fb e8 52 2a 1f e1 48 8b bb a0 02 00 00 e8 46 59 1f e1 48 8b 83 a0 02 00 00 5b <48> 8b 38 e9 26 9a fe e0 66 0f 1f 44 00 00 66 66 66 66 90 48 8b
    RIP [<ffffffffa019da92>] edac_unregister_sysfs+0x22/0x30 [edac_core]
    RSP <ffff88030da3fe28>

    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
    Fixes: 7a623c039075 ("edac: rewrite the sysfs code to use struct device")
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/edac/edac_mc_sysfs.c | 21 ++++++++++++++-------
    1 file changed, 14 insertions(+), 7 deletions(-)

    --- a/drivers/edac/edac_mc_sysfs.c
    +++ b/drivers/edac/edac_mc_sysfs.c
    @@ -880,21 +880,26 @@ static struct device_type mci_attr_type
    int edac_create_sysfs_mci_device(struct mem_ctl_info *mci,
    const struct attribute_group **groups)
    {
    + char *name;
    int i, err;

    /*
    * The memory controller needs its own bus, in order to avoid
    * namespace conflicts at /sys/bus/edac.
    */
    - mci->bus->name = kasprintf(GFP_KERNEL, "mc%d", mci->mc_idx);
    - if (!mci->bus->name)
    + name = kasprintf(GFP_KERNEL, "mc%d", mci->mc_idx);
    + if (!name)
    return -ENOMEM;

    + mci->bus->name = name;
    +
    edac_dbg(0, "creating bus %s\n", mci->bus->name);

    err = bus_register(mci->bus);
    - if (err < 0)
    - goto fail_free_name;
    + if (err < 0) {
    + kfree(name);
    + return err;
    + }

    /* get the /sys/devices/system/edac subsys reference */
    mci->dev.type = &mci_attr_type;
    @@ -961,8 +966,8 @@ fail_unregister_dimm:
    device_unregister(&mci->dev);
    fail_unregister_bus:
    bus_unregister(mci->bus);
    -fail_free_name:
    - kfree(mci->bus->name);
    + kfree(name);
    +
    return err;
    }

    @@ -993,10 +998,12 @@ void edac_remove_sysfs_mci_device(struct

    void edac_unregister_sysfs(struct mem_ctl_info *mci)
    {
    + const char *name = mci->bus->name;
    +
    edac_dbg(1, "Unregistering device %s\n", dev_name(&mci->dev));
    device_unregister(&mci->dev);
    bus_unregister(mci->bus);
    - kfree(mci->bus->name);
    + kfree(name);
    }

    static void mc_attr_release(struct device *dev)
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