Messages in this thread | | | Date | Tue, 27 Apr 2021 18:12:17 +0200 | From | Greg KH <> | Subject | Re: [PATCH 167/190] Revert "gdrom: fix a memory leak bug" |
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On Tue, Apr 27, 2021 at 08:39:15AM -0600, Jens Axboe wrote: > On 4/27/21 8:03 AM, Peter Rosin wrote: > > On 2021-04-27 15:01, Greg KH wrote: > >> On Fri, Apr 23, 2021 at 08:20:30AM -0600, Jens Axboe wrote: > >>> On 4/22/21 3:29 PM, Peter Rosin wrote: > >>>>> This reverts commit 093c48213ee37c3c3ff1cf5ac1aa2a9d8bc66017. > >>>> > >>>> The reverted patch looks fishy. > >>>> > >>>> gc.cd_info is kzalloc:ed on probe. In case probe fails after this allocation, the > >>>> memory is kfree:d but the variable is NOT zeroed out. > >>>> > >>>> AFAICT, the above leads to a double-free on exit by the added line. > >>>> > >>>> I believe gd.cd_info should be kfree:d on remove instead. > >>>> > >>>> However, might not gc.toc also be kfree:d twice for similar reasons? > >>>> > >>>> I could easily be mistaken. > >>> > >>> >From taking a quick look the other day, that's my conclusion too. I > >>> don't think the patch is correct, but I don't think the surrounding code > >>> is correct right now either. > >> > >> Thanks for the review from both of you, I'll keep this commit in the > >> tree. > > Err, which commit is "this" and what tree are you keeping it in? I > > think you mean that you are keeping the revert in your tree with > > reverts, and not that you mean that we should keep the original > > commit in Linus' tree. > > > > In any case, I'd think that the original memory leak is somewhat > > better than the introduced double-free and therefore the revert > > should be done. > > It should probably look like the below, though I doubt it matters > since only one device is supported anyway. As long as the free > happens post unregister, it likely won't make a difference. But > it is cleaner and easier to verify, and should double device support > ever be introduced, the existing code is buggy. > > But given that, I don't think we should keep the revert patch. > > diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c > index 9874fc1c815b..02d369881165 100644 > --- a/drivers/cdrom/gdrom.c > +++ b/drivers/cdrom/gdrom.c > @@ -831,6 +831,8 @@ static int remove_gdrom(struct platform_device *devptr) > if (gdrom_major) > unregister_blkdev(gdrom_major, GDROM_DEV_NAME); > unregister_cdrom(gd.cd_info); > + kfree(gd.toc); > + kfree(gd.cd_info); > > return 0; > } > @@ -862,8 +864,6 @@ static void __exit exit_gdrom(void) > { > platform_device_unregister(pd); > platform_driver_unregister(&gdrom_driver); > - kfree(gd.toc); > - kfree(gd.cd_info); > } > > module_init(init_gdrom); > > -- > Jens Axboe >
I'll add this fix to the tree after the revert, and give you the credit for the fix :)
thanks,
greg k-h
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