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Task_t considered harmful

googleprojectzero.blogspot.com

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Re: Task_t considered harmful

#31

Post by cormacrelf »

a-no-n wrote: post #2

Ever since installing 10.12.1, I've been having a bunch of processes randomly entering a quasi-paused SIGSTOP-ish state (neither closable, apps not "bouncing" (loading) and just not responding. Running Instruments, correlating logs and such doesn't identify any clear cause. I'm having to `sudo kill -CONT -1` in order to get things moving again. I'm wondering if it's related to XNU mitigations or just some spurious "s…

I did exactly this when my Mac ran out of memory yesterday. Safari hung with a 'your computer is running out of memory' warning (168 tabs open!) and I didn't want to lose them all by force quitting. But the Safari process itself wasn't "Not Responding" and we were back to 0% CPU.

So I quit everything else, SIGCONT'd Safari, and it started responding again, so I tried unsuccessfully to close some tabs. Of course, Safari somewhat isolates pages in separate processes, so I ran `ps aux | grep WebContent | grep -v grep | cut -d' ' -f11 | xargs kill -SIGCONT` as well.

It all sprang back to life, and all the tabs I'd shut in vain zipped away. Got that one saved for later. It's probably easier just to use -1 now I've learned what that is!

I do wonder what's suspending these processes indefinitely. I should have done more inspection to see what state they were in. I'm not familiar with how WebKit content threads communicate though, so that's for another day.

Re: Task_t considered harmful

#32

Post by 0x0 »

blumentopf wrote: post #30
blinkingled wrote: post #12

Earlier quoted context omitted.

Yeah - the failed mitigations followed by a "long term" fix was interesting as well. Apple literally had to change execve() this late in the OS's development cycle to allocate new task and thread structs(that's two extra allocations and copies in hot path!) to fix it for good. That this design problem lingered around for so long doesn't look good for Apple - it's one thing for a use after free bug in obscure piece of…

Business as usual with macOS. The other day I was browsing the ocspd source code. Turns out it calls openssl using system(). So openssl is officially deprecated on macOS and yet they're using it internally to handle certificates?! And there's an enlightening comment: /* Given a path to a DER-encoded CRL file and a path to a PEM-encoded * CA issuers file, use OpenSSL to validate the CRL. This is a hack, * necessitated…

o.O

Re: Task_t considered harmful

#34

Post by zimpenfish »

blumentopf wrote: post #30
blinkingled wrote: post #12

Earlier quoted context omitted.

Yeah - the failed mitigations followed by a "long term" fix was interesting as well. Apple literally had to change execve() this late in the OS's development cycle to allocate new task and thread structs(that's two extra allocations and copies in hot path!) to fix it for good. That this design problem lingered around for so long doesn't look good for Apple - it's one thing for a use after free bug in obscure piece of…

Business as usual with macOS. The other day I was browsing the ocspd source code. Turns out it calls openssl using system(). So openssl is officially deprecated on macOS and yet they're using it internally to handle certificates?! And there's an enlightening comment: /* Given a path to a DER-encoded CRL file and a path to a PEM-encoded * CA issuers file, use OpenSSL to validate the CRL. This is a hack, * necessitated…

Linking to openssl was deprecated (lack of binary stability) - not the command line tools.

Re: Task_t considered harmful

#35

Post by mikeash »

blumentopf wrote: post #30
blinkingled wrote: post #12

Earlier quoted context omitted.

Yeah - the failed mitigations followed by a "long term" fix was interesting as well. Apple literally had to change execve() this late in the OS's development cycle to allocate new task and thread structs(that's two extra allocations and copies in hot path!) to fix it for good. That this design problem lingered around for so long doesn't look good for Apple - it's one thing for a use after free bug in obscure piece of…

Business as usual with macOS. The other day I was browsing the ocspd source code. Turns out it calls openssl using system(). So openssl is officially deprecated on macOS and yet they're using it internally to handle certificates?! And there's an enlightening comment: /* Given a path to a DER-encoded CRL file and a path to a PEM-encoded * CA issuers file, use OpenSSL to validate the CRL. This is a hack, * necessitated…

I don't see a major problem with using the openssl command for this, but using system() to do it is completely insane.

Re: Task_t considered harmful

#37

Post by gulpahum »

drinchev wrote: post #8

I'm still with 10.11. I don't plan to update soon, since the benefit of Siri, Photos and the other major features is quite small, compared to the risk that I might loose working days if something goes wrong ( I'm a freelancer ). As far as I read in the article there will be 10.12.1 ( the final fix ) which will have that part of the kernel refactored. I hope Apple will also support 10.11 and issue an update with the s…

I got an update to 10.11 El Capitan yesterday, which probably fixes the vulnerability. You can see the fix in Apple's support page, have a look at the bottom of the page about "System Boot":

https://support.apple.com/en-us/HT207275

It looks like even 10.10 Yosemite got a fix. Here's a full list of security fixes Apple has made to its software:

https://support.apple.com/en-us/HT201222

Re: Task_t considered harmful

#38

Post by wyager »

blumentopf wrote: post #30
blinkingled wrote: post #12

Earlier quoted context omitted.

Yeah - the failed mitigations followed by a "long term" fix was interesting as well. Apple literally had to change execve() this late in the OS's development cycle to allocate new task and thread structs(that's two extra allocations and copies in hot path!) to fix it for good. That this design problem lingered around for so long doesn't look good for Apple - it's one thing for a use after free bug in obscure piece of…

Business as usual with macOS. The other day I was browsing the ocspd source code. Turns out it calls openssl using system(). So openssl is officially deprecated on macOS and yet they're using it internally to handle certificates?! And there's an enlightening comment: /* Given a path to a DER-encoded CRL file and a path to a PEM-encoded * CA issuers file, use OpenSSL to validate the CRL. This is a hack, * necessitated…

Apple needs to take a bit of those tens of billions of dollars they have sitting around and spend it on starting from scratch with something that's not horrifically crufty. The quality of their software is lagging so far behind the quality of their hardware right now. Realistically, I think we may just be at the point where operating systems and all the stuff the companies put on top of them are too complicated to keep developing in the traditional way with traditional tools. Formal verification might be the cheapest way forward at this point.

Re: Task_t considered harmful

#39

Post by kevingadd »

blinkingled wrote: post #12
0x0 wrote: post #11

Copying my comment from the earlier submission that didn't gain much traction here: What an absolutely amazing tour-de-force of a devastating design flaw in all versions of macOS and iOS and tvOS and watchOS! The negotiations detailed in the bug report timeline about meetings between "senior apple and google leadership" for keeping this secret past the general deadline really underlines that.

Yeah - the failed mitigations followed by a "long term" fix was interesting as well. Apple literally had to change execve() this late in the OS's development cycle to allocate new task and thread structs(that's two extra allocations and copies in hot path!) to fix it for good. That this design problem lingered around for so long doesn't look good for Apple - it's one thing for a use after free bug in obscure piece of…

Incidentally the huge set of problems with execve were very old news - I know a developer who tried to get them fixed (because they affected a piece of Apple software) and failed. Presumably this was because execve bugs were considered unimportant.

Oops!

Re: Task_t considered harmful

#40

Post by JoeAltmaier »

wyager wrote: post #38
blumentopf wrote: post #30

Earlier quoted context omitted.

Business as usual with macOS. The other day I was browsing the ocspd source code. Turns out it calls openssl using system(). So openssl is officially deprecated on macOS and yet they're using it internally to handle certificates?! And there's an enlightening comment: /* Given a path to a DER-encoded CRL file and a path to a PEM-encoded * CA issuers file, use OpenSSL to validate the CRL. This is a hack, * necessitated…

Apple needs to take a bit of those tens of billions of dollars they have sitting around and spend it on starting from scratch with something that's not horrifically crufty. The quality of their software is lagging so far behind the quality of their hardware right now. Realistically, I think we may just be at the point where operating systems and all the stuff the companies put on top of them are too complicated to ke…

Hundreds of billions?
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