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Differential D35553

protect arm busdma bounce page counters with bounce page lock
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Authored by • hselasky on Jun 22 2022, 11:23 PM.
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mjg
jhb
rfyu28uyeg_snkmail.com
• hselasky
andrew
Commits
rG78088c5714e0: busdma: Protect ARM busdma bounce page counters using the bounce page lock.
rGa0ffae30c593: busdma: Protect ARM busdma bounce page counters using the bounce page lock.
rG6c4b6f55f77d: busdma: Protect ARM busdma bounce page counters using the bounce page lock.
Summary

In bus_dmamap_unload(), the counters for free_bpages and reserved_bpages appear to be vulnerable to unprotected read-modify-write operations that result in accounting that looks like a page leak.

See also https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=264836

Please suggest appropriate reviewers.

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Event Timeline

rfyu28uyeg_snkmail.com created this revision.Jun 22 2022, 11:23 PM
Herald added subscribers: andrew, imp. · View Herald TranscriptJun 22 2022, 11:23 PM
rfyu28uyeg_snkmail.com requested review of this revision.Jun 22 2022, 11:23 PM
• hselasky accepted this revision.Jun 23 2022, 8:34 AM

Looks good.

This revision is now accepted and ready to land.Jun 23 2022, 8:34 AM
• hselasky added a comment.Jun 23 2022, 9:33 AM

I've suggested some optimizations. Have a look at the PR.

• hselasky commandeered this revision.Jun 23 2022, 7:20 PM
• hselasky edited reviewers, added: rfyu28uyeg_snkmail.com; removed: • hselasky.
This revision now requires review to proceed.Jun 23 2022, 7:20 PM
• hselasky updated this revision to Diff 107327.Jun 23 2022, 7:21 PM

Updated patch a bit. Maybe this piece of code can be removed altogether ...

• hselasky accepted this revision.Jun 23 2022, 7:21 PM
This revision is now accepted and ready to land.Jun 23 2022, 7:21 PM
• hselasky added a reviewer: andrew.Jun 23 2022, 7:23 PM

Andrew: Do you have time to have a quick look here?

andrew added a comment.Jun 24 2022, 3:07 PM

It looks correct, however I don't know much about the 32-bit arm busdma code.

Closed by commit rG6c4b6f55f77d: busdma: Protect ARM busdma bounce page counters using the bounce page lock. (authored by • hselasky). · Explain WhyJun 25 2022, 10:07 AM
This revision was automatically updated to reflect the committed changes.
• hselasky added a commit: rG6c4b6f55f77d: busdma: Protect ARM busdma bounce page counters using the bounce page lock..
• hselasky added a commit: rGa0ffae30c593: busdma: Protect ARM busdma bounce page counters using the bounce page lock..Jun 28 2022, 6:20 AM
• hselasky added a commit: rG78088c5714e0: busdma: Protect ARM busdma bounce page counters using the bounce page lock..

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sys/
arm/
arm/
2 lines

Diff 107262

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sys/arm/arm/busdma_machdep.c

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