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    Subject[ 032/221] SCSI: prevent stack buffer overflow in host_reset
    Date
    3.7-stable review patch.  If anyone has any objections, please let me know.

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

    From: Sasha Levin <sasha.levin@oracle.com>

    commit 072f19b4bea31cdd482d79f805413f2f9ac9e233 upstream.

    store_host_reset() has tried to re-invent the wheel to compare sysfs strings.
    Unfortunately it did so poorly and never bothered to check the input from
    userspace before overwriting stack with it, so something simple as:

    echo "WoopsieWoopsie" >
    /sys/devices/pseudo_0/adapter0/host0/scsi_host/host0/host_reset

    would result in:

    [ 316.310101] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81f5bac7
    [ 316.310101]
    [ 316.320051] Pid: 6655, comm: sh Tainted: G W 3.7.0-rc5-next-20121114-sasha-00016-g5c9d68d-dirty #129
    [ 316.320051] Call Trace:
    [ 316.340058] pps pps0: PPS event at 1352918752.620355751
    [ 316.340062] pps pps0: capture assert seq #303
    [ 316.320051] [<ffffffff83b3856b>] panic+0xcd/0x1f4
    [ 316.320051] [<ffffffff81f5bac7>] ? store_host_reset+0xd7/0x100
    [ 316.320051] [<ffffffff8110b996>] __stack_chk_fail+0x16/0x20
    [ 316.320051] [<ffffffff81f5bac7>] store_host_reset+0xd7/0x100
    [ 316.320051] [<ffffffff81e55bb3>] dev_attr_store+0x13/0x30
    [ 316.320051] [<ffffffff812f7db1>] sysfs_write_file+0x101/0x170
    [ 316.320051] [<ffffffff8127acc8>] vfs_write+0xb8/0x180
    [ 316.320051] [<ffffffff8127ae80>] sys_write+0x50/0xa0
    [ 316.320051] [<ffffffff83c03418>] tracesys+0xe1/0xe6

    Fix this by uninventing whatever was going on there and just use sysfs_streq.

    Bug introduced by 29443691 ("[SCSI] scsi: Added support for adapter and
    firmware reset").

    [jejb: added necessary const to prevent compile warnings]
    Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
    Signed-off-by: James Bottomley <JBottomley@Parallels.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/scsi/scsi_sysfs.c | 11 ++++-------
    1 file changed, 4 insertions(+), 7 deletions(-)

    --- a/drivers/scsi/scsi_sysfs.c
    +++ b/drivers/scsi/scsi_sysfs.c
    @@ -247,11 +247,11 @@ show_shost_active_mode(struct device *de

    static DEVICE_ATTR(active_mode, S_IRUGO | S_IWUSR, show_shost_active_mode, NULL);

    -static int check_reset_type(char *str)
    +static int check_reset_type(const char *str)
    {
    - if (strncmp(str, "adapter", 10) == 0)
    + if (sysfs_streq(str, "adapter"))
    return SCSI_ADAPTER_RESET;
    - else if (strncmp(str, "firmware", 10) == 0)
    + else if (sysfs_streq(str, "firmware"))
    return SCSI_FIRMWARE_RESET;
    else
    return 0;
    @@ -264,12 +264,9 @@ store_host_reset(struct device *dev, str
    struct Scsi_Host *shost = class_to_shost(dev);
    struct scsi_host_template *sht = shost->hostt;
    int ret = -EINVAL;
    - char str[10];
    int type;

    - sscanf(buf, "%s", str);
    - type = check_reset_type(str);
    -
    + type = check_reset_type(buf);
    if (!type)
    goto exit_store_host_reset;




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