iceberg wrote:
KERNEL_VERSION: 2.6.31
DESCRIBE:
Driver sg.c might sleep in atomic context, because it calls
scsi_device_put under lock_kernel.
/drivers/scsi/sg.c:306:
static int
sg_open(struct inode *inode, struct file *filp)
{
...
lock_kernel();
...
error_out:
if (retval)
scsi_device_put(sdp->device);
...
Path to might_sleep macro from scsi_device_put:
1. scsi_device_put calls put_device at ./drivers/scsi/scsi.c:1111
2. put_device calls kobject_put at ./drivers/base/core.c:1038
3. kobject_put calls kref_put at ./lib/kobject.c
4. kref_put may call callback function kobject_release at ./lib/kref.c if
refcount becomes zero, which might_sleep because it calls user event. Details:
5.1 kobject_cleanup calls kobject_uevent at ./lib/kobject.c:555
5.2 kobject_uevent calls kobject_uevent_env at ./lib/kobject_uevent.c:282
5.3 kobject_uevent_env calls call_usermodehelper_exec at
include/linux/kmod.h:83
5.4 call_usermodehelper_exec calls wait_for_completion at ./kernel/kmod.c:481
5.5 wait_for_completion calls wait_for_common at ./kernel/sched.c:5710
5.6 wait_for_common calls might_sleep at ./kernels/sched.c:5692
Found by: Linux Driver Verification
This patch to sg_open() does one (and only one) unlock_kernel()
prior to scsi_device_put(). I presume sg_put_dev() may also
sleep so the unlock_kernel() is moved before it as well.
Hopefully Tomo will comment.
Doug Gilbert
--- linux/drivers/scsi/sg.c2631 2009-09-10 06:22:34.000000000 -0400
+++ linux/drivers/scsi/sg.c 2009-10-01 15:54:30.000000000 -0400
@@ -227,8 +227,10 @@
Sg_fd *sfp;
int res;
int retval;
+ int locked = 0;
lock_kernel();
+ locked = 1;
nonseekable_open(inode, filp);
SCSI_LOG_TIMEOUT(3, printk("sg_open: dev=%d, flags=0x%x\n", dev, flags));
sdp = sg_get_dev(dev);
@@ -302,12 +304,16 @@
}
retval = 0;
error_out:
- if (retval)
+ if (retval) {
+ unlock_kernel();
+ locked = 0;
scsi_device_put(sdp->device);
+ }
sg_put:
+ if (locked)
+ unlock_kernel();
if (sdp)
sg_put_dev(sdp);
- unlock_kernel();
return retval;
}
--
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