Date: Sun, 03 Jul 2005 00:40:04 -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: <422DBD0F.2070206@DeepCore.dk> In-Reply-To: <422DBA9E.8060502@root.org> References: <422225D6.5020009@root.org> <422D84FF.1010707@DeepCore.dk> <422DBA9E.8060502@root.org>
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Nate Lawson wrote: > S=F8ren Schmidt wrote: >=20 >> Nate Lawson wrote: >> >>> If you've been having "memory modified after free" panics on -current= =20 >>> and have a Thinkpad, the attached patch should fix things for you. A= =20 >>> quick check of RELENG_5 indicates that the bug is probably there also= =20 >>> but I haven't tested for it there. >>> >>> The bug is triggered by timeouts in the ata_getparam() probe path. =20 >>> The ata_timeout() fires and ata_end_transaction() is called to get=20 >>> the status. However, it continues down into ata_pio_read() even=20 >>> though there is no data available since we had a timeout, not read=20 >>> completion. ata_pio_read() reads 512 bytes of probably bogus=20 >>> data. The important problem is that it also advances donecount. On = >>> subsequent timeouts (note there are 4 below), donecount advances into= =20 >>> unallocated memory and so subsequent ata_pio_read() calls overwrite=20 >>> 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=20 >>> 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=20 >>> way to proceed for unwinding DMA state and the like for the other=20 >>> cases. This is enough to fix the overwrite and subsequent panic on my= =20 >>> systems. I've run heavy IO stress and DVD accesses for a while and=20 >>> no further panics. >>> >>> While looking into this, I found another potential problem. In one=20 >>> reinjection case, donecount wasn't reset to 0. The patch for=20 >>> ata-queue.c does this and I think it's necessary but don't hit this=20 >>> 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=20 >>> archives for this: >>> http://lists.freebsd.org/mailman/htdig/freebsd-current/2004-August/03= 3033.html=20 >> >> >> >> >> 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 :)) >=20 >=20 > Nope, but I'm glad you can corroborate these fixes are correct. Actually I cant, I havn't looked at what was committed since I already=20 did fix these problems in the mkIII patches floating around.. Anyhow its in there and the committer has to deal with it until/if I=20 commit mkIII to -current, I'm out of the loop until then... --=20 -S=F8ren _______________________________________________ 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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