Hi, >-----Original Message----- >From: linux-omap-ow...@vger.kernel.org [mailto:linux-omap- >ow...@vger.kernel.org] On Behalf Of Felipe Contreras >Sent: Tuesday, February 09, 2010 6:30 AM >To: Ameya Palande >Cc: linux-omap@vger.kernel.org; Ramirez Luna, Omar; Menon, Nishanth; >Chitriki Rudramuni, Deepak; felipe.contre...@nokia.com; ext- >phil.2.carm...@nokia.com >Subject: Re: [PATCH] DSPBRIDGE: Prevent memory corruption in >DRV_ProcFreeDMMRes > >On Mon, Feb 8, 2010 at 10:25 PM, Ameya Palande <ameya.pala...@nokia.com> >wrote: >> Background: bridge_close() has the responsibility to cleanup all the >> resources allocated by user space process. One of those resources is >> DMMRes which is used for tracking DMM resource allocation done in >> PROC_Map() and PROC_UnMap(). >> >> DRV_ProcFreeDMMRes() function was used for cleaning up DMMRes has >following >> problems which are fixed by this patch: >> >> 1. It access and modifies pDMMRes pointer when it is already freed by >> PROC_UnMap() >> 2. Instead of passing ulDSPAddr it passes ulDSPResAddr to PROC_UnMap() >which >> will not retrive correct DMMRes element. > >This patch is doing the right thing to me, however, it's a bit >difficult to review because it's doing many changes at once. > >Personally I would > 1) Fix the wrong dereferences in DRV_ProcFreeDMMRes >[at this point the bug should be fixed] >[the leaks would be freed by the outer loop] > > 2) Fix the wrong PROC_UnMap address passed in DRV_ProcFreeDMMRes > 3) Remove the unnecessary outer loop in DRV_RemoveAllDMMResElements >[at this point the code would actually make sense] > > 4) Merge DRV_ProcFreeDMMRes into DRV_RemoveAllDMMResElements > 5) Improve coding style > >The end result would be the same, but easier to see what's going on :) > >Cheers. > >-- >Felipe Contreras
The root problem here is that remove the DMM element should be in PROC_UnMap but in PROC_UnReserveMemory, because apart of the problem your are seeing about memory corruption if the application does a PROC_ReserveMemory and then it finished unexpectedly the resource cleanup wont be able to unreserved the memory because there is no a DMMres element in process context struct, the same applies in the case of application calls PROC_ReserveMemory, PROC_Map, PROC_UnMap but fails to do the PROC_UnReserveMemory. So the right solution should be: 1 .- Remove DRV_InsertDMMResElement function from PROC_Map and put it on PROC_ReserveMemory. 2.- Keep DRV_UpdateDMMResElement function in PROC_Map. 3.- Remove DRV_RemoveDMMResElement function from PROC_UnMap and put it on ROC_UnReserveMemory function. 4.- Clear dmmAllocated flag in PROC_UnMap: pDMMRes->dmmAllocated = 0; 5 .- in the function DRV_ProcFreeDMMRes, call PROC_UnMap "if (pDMMRes->dmmAllocated)" and always call PROC_UnReserveMemory not in this point is not needed the save hProcessor nor ulDSPResAddr addresses. 6 .- cleanup DRV_RemoveAllDMMResElements function (while loop is not needed). Regards, Fernando. >-- >To unsubscribe from this list: send the line "unsubscribe linux-omap" in >the body of a message to majord...@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
