----- Original Message -----
> From: "Milan P. Gandhi" <mgandhi@xxxxxxxxxx>
> To: linux-scsi@xxxxxxxxxxxxxxx
> Cc: "Laurence Oberman" <loberman@xxxxxxxxxx>, "chad dupuis" <chad.dupuis@xxxxxxxxxx>
> Sent: Saturday, December 24, 2016 11:32:46 AM
> Subject: [PATCH] qla2xxx: Get mutex lock before checking optrom_state
>
> 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 <mgandhi@xxxxxxxxxx>
> Signed-off-by: Milan P. Gandhi <mgandhi@xxxxxxxxxx>
> ---
> 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);
>
>
Looks good, and I know it fixed the issue.
Milan, Thank you for this work.
Reviewed-by: Laurence Oberman <loberman@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
