Hi Milan,
On 12/24/16, 8:32 AM, "linux-scsi-ow...@vger.kernel.org on behalf of Milan P.
Gandhi" <linux-scsi-ow...@vger.kernel.org on behalf of mgan...@redhat.com>
wrote:
>Hello,
>
>There is a race condition with qla2xxx optrom functions where
>one thread might modify optrom buffer, optrom_state while
>other thread is still reading from it.
>
>In couple of crashes, it was found that we had successfully
>passed the following 'if' check where we confirm optrom_state
>to be QLA_SREADING. But by the time we acquired mutex lock
>to proceed with memory_read_from_buffer function, some other
>thread/process had already modified that option rom buffer
>and optrom_state from QLA_SREADING to QLA_SWAITING. Then
>we got ha->optrom_buffer 0x0 and crashed the system:
>
> if (ha->optrom_state != QLA_SREADING)
> return 0;
>
> mutex_lock(&ha->optrom_mutex);
> rval = memory_read_from_buffer(buf, count, &off, ha->optrom_buffer,
> ha->optrom_region_size);
> mutex_unlock(&ha->optrom_mutex);
>
>
>With current optrom function we get following crash due to
>a race condition:
>
>[ 1479.466679] BUG: unable to handle kernel NULL pointer dereference at
> (null)
>[ 1479.466707] IP: [<ffffffff81326756>] memcpy+0x6/0x110
>[...]
>[ 1479.473673] Call Trace:
>[ 1479.474296] [<ffffffff81225cbc>] ? memory_read_from_buffer+0x3c/0x60
>[ 1479.474941] [<ffffffffa01574dc>] qla2x00_sysfs_read_optrom+0x9c/0xc0
>[qla2xxx]
>[ 1479.475571] [<ffffffff8127e76b>] read+0xdb/0x1f0
>[ 1479.476206] [<ffffffff811fdf9e>] vfs_read+0x9e/0x170
>[ 1479.476839] [<ffffffff811feb6f>] SyS_read+0x7f/0xe0
>[ 1479.477466] [<ffffffff816964c9>] system_call_fastpath+0x16/0x1b
>
>
>Below patch modifies qla2x00_sysfs_read_optrom,
>qla2x00_sysfs_write_optrom functions to get the mutex_lock
>before checking ha->optrom_state to avoid similar crashes.
>
>The patch was applied and tested and same crashes were no
>longer observed again.
>
>
>Tested-by: Milan P. Gandhi <mgan...@redhat.com>
>Signed-off-by: Milan P. Gandhi <mgan...@redhat.com>
>---
> drivers/scsi/qla2xxx/qla_attr.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/scsi/qla2xxx/qla_attr.c b/drivers/scsi/qla2xxx/qla_attr.c
>index da5ae11..47ea164 100644
>--- a/drivers/scsi/qla2xxx/qla_attr.c
>+++ b/drivers/scsi/qla2xxx/qla_attr.c
>@@ -329,12 +329,15 @@ qla2x00_sysfs_read_optrom(struct file *filp, struct
>kobject *kobj,
> struct qla_hw_data *ha = vha->hw;
> ssize_t rval = 0;
>
>+ mutex_lock(&ha->optrom_mutex);
>+
> if (ha->optrom_state != QLA_SREADING)
>- return 0;
>+ goto out;
>
>- mutex_lock(&ha->optrom_mutex);
> rval = memory_read_from_buffer(buf, count, &off, ha->optrom_buffer,
> ha->optrom_region_size);
>+
>+out:
> mutex_unlock(&ha->optrom_mutex);
>
> return rval;
>@@ -349,14 +352,19 @@ qla2x00_sysfs_write_optrom(struct file *filp, struct
>kobject *kobj,
> struct device, kobj)));
> struct qla_hw_data *ha = vha->hw;
>
>- if (ha->optrom_state != QLA_SWRITING)
>+ mutex_lock(&ha->optrom_mutex);
>+
>+ if (ha->optrom_state != QLA_SWRITING) {
>+ mutex_unlock(&ha->optrom_mutex);
> return -EINVAL;
>- if (off > ha->optrom_region_size)
>+ }
>+ if (off > ha->optrom_region_size) {
>+ mutex_unlock(&ha->optrom_mutex);
> return -ERANGE;
>+ }
> if (off + count > ha->optrom_region_size)
> count = ha->optrom_region_size - off;
>
>- mutex_lock(&ha->optrom_mutex);
> memcpy(&ha->optrom_buffer[off], buf, count);
> mutex_unlock(&ha->optrom_mutex);
>
>--
Thanks for the Patch. This looks good.
Acked-by: Himanshu Madhani <himanshu.madh...@cavium.com>
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