From c7702b8c22712a06080e10f1d2dee1a133ec8809 Mon Sep 17 00:00:00 2001 From: "Milan P. Gandhi" Date: Sat, 24 Dec 2016 22:02:46 +0530 Subject: [PATCH] scsi: qla2xxx: Get mutex lock before checking optrom_state 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: [] memcpy+0x6/0x110 [...] [ 1479.473673] Call Trace: [ 1479.474296] [] ? memory_read_from_buffer+0x3c/0x60 [ 1479.474941] [] qla2x00_sysfs_read_optrom+0x9c/0xc0 [qla2xxx] [ 1479.475571] [] read+0xdb/0x1f0 [ 1479.476206] [] vfs_read+0x9e/0x170 [ 1479.476839] [] SyS_read+0x7f/0xe0 [ 1479.477466] [] 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 Signed-off-by: Milan P. Gandhi Reviewed-by: Laurence Oberman Acked-by: Himanshu Madhani Signed-off-by: Martin K. Petersen --- 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 47eb4d545d13..83f8527c0363 100644 --- a/drivers/scsi/qla2xxx/qla_attr.c +++ b/drivers/scsi/qla2xxx/qla_attr.c @@ -243,12 +243,15 @@ 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; @@ -263,14 +266,19 @@ 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); -- 2.39.5