> -----Original Message----- > From: Dan Carpenter [mailto:dan.carpenter@xxxxxxxxxx] > Sent: Thursday, May 12, 2016 12:05 PM > To: Petros Koutoupis > Cc: Sumit Saxena; Finn Thain; kashyap.desai@xxxxxxxxxxxxx; > sumit.saxena@xxxxxxxxxxxxx; uday.lingala@xxxxxxxxxxxxx; > megaraidlinux.pdl@xxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] megaraid: add scsi_cmnd NULL check before use > > On Wed, May 11, 2016 at 08:49:51PM -0500, Petros Koutoupis wrote: > > Sumit, > > > > I will resubmit the patch with all the recommendations. Thank you. In > > case you are interested, I have a crash file showcasing the error. I > > can always provide this outside of this mailing thread. > > > > Please send it to the thread. > > To be honest, I totally can't understand this thread. Sumit says it is impossible > and you are saying that you have seen it happen in real life. > Are you using out of tree code or something? What are you doing that is > unexpected? > > I don't see the point of adding a WARN_ON(). NULL derefs normally generate a > pretty clear stack trace already (unless they are caused by memory corruption). > Why are we not just fixing the bugs instead of warning and then crashing. Agree, if there scsi_cmnd is coming as NULL, please attach logs. I will look into them. > > Also when I'm doing static analysis people always tell me that "that bug is > impossible, trust me." and instead of trusting people I really wish they would just > show me the relevant code that prevents it from happening. Inside megasas_build_io_fusion() function, driver sets "cmd->scmd" pointer(SCSI command pointer received from SCSI mid layer). Functions called inside megasas_build_io_fusion()(which actually builds frame to be sent to firmware) are setting Function type- MPI2_FUNCTION_SCSI_IO_REQUEST (or) MEGASAS_MPI2_FUNCTION_LD_IO_REQUEST. So in case Function type set to any one these two, there must be valid "cmd->scmd". Thanks, Sumit > > regards, > dan carpenter -- 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
