Date: Sun, 03 Jul 2005 00:39:53 -0000 From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@DeepCore.dk> To: Nate Lawson <nate@root.org> Cc: stable@freebsd.org, current@freebsd.org Subject: Re: patch: fix ata panic with Thinkpad CD and DVD drives Message-ID: <422D84FF.1010707@DeepCore.dk> In-Reply-To: <422225D6.5020009@root.org> References: <422225D6.5020009@root.org>
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Nate Lawson wrote: > If you've been having "memory modified after free" panics on -current > and have a Thinkpad, the attached patch should fix things for you. A > quick check of RELENG_5 indicates that the bug is probably there also > but I haven't tested for it there. > > The bug is triggered by timeouts in the ata_getparam() probe path. The > ata_timeout() fires and ata_end_transaction() is called to get the > status. However, it continues down into ata_pio_read() even though > there is no data available since we had a timeout, not read completion. > ata_pio_read() reads 512 bytes of probably bogus data. The important > problem is that it also advances donecount. On subsequent timeouts > (note there are 4 below), donecount advances into unallocated memory and > so subsequent ata_pio_read() calls overwrite 512 bytes of someone else's > memory. > > The fix is to exit immediately if ATA_R_TIMEOUT is set after reading the > status in ata_end_transaction(). It shouldn't go into ata_pio_read() if > there was a timeout. The patch does this. > > However, it only handles PIO timeouts since I wasn't sure the best way > to proceed for unwinding DMA state and the like for the other cases. > This is enough to fix the overwrite and subsequent panic on my systems. > I've run heavy IO stress and DVD accesses for a while and no further > panics. > > While looking into this, I found another potential problem. In one > reinjection case, donecount wasn't reset to 0. The patch for > ata-queue.c does this and I think it's necessary but don't hit this case > in testing so I can't be sure. Finally, there's one whitespace nit that > helps with clarity. > > These are similar bugs to one found back in August that had the same > effect. Here's the closest reference I could find in the mail archives > for this: > http://lists.freebsd.org/mailman/htdig/freebsd-current/2004-August/033033.html Just a note from here, these bugs are fixed in ATA mkIII so you could just have gleaned the solution from there (or maybe you did :)) -- -Søren _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
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