Explaining Dirty Cow - Computerphile

Dirty Cow is a serious security flaw. Dr Steve Bagley takes us through the details.

This video was filmed and edited by Sean Riley.

[LittleBungorf]

we just covered linux memory management in my os class yesterday. It's so neat having concrete examples of what you're learning, especially as timely as this is.

[Epinardscaramel]

I don't understand bugs if they're not explained by Tom Scott.

[CashewOCE]

I feel like the explanation about memory wasn't concise and well-explained. I didn't follow anything; could just be me though.

[TeganBurns]

That is some dirty thread handling, especially for something so important!!

[DusteDdekay]

Nice explaination, I had to find the source after seeing the first on the subject. It is relevant to note that in order for the overwritten (compromised) file to actually execute the root shell, it needs to have the SUID bit set in its file-permissions. Overwriting any old file won't work, but programs such as passwd and sudo are targets because they need the SUID bit to actually work.

[fz]

It would be awesome if you could explain how they fixed it since it looks like a design weakness more than a simple patcheable bug.

[apinakapinastorba]

8:27 For a moment I thought you said "use it to run a .NET", phew.

[stale]

This is great news for everyone with an android phone that no longer gets updates.

[TheNefari]

What is that sound at 3:07 also comes some time before

[ninjafruitchilled]

I didn't really follow how writing to the memory page files lets you write to other files, like the root password file?

[xbaadfd]

Saw first ? Go here 1:13 : Go here 0:00;

[kevincozens]

I always find it interesting to see the tractor feed paper that is used when explaining some of the topics discussed in Computerphile. I haven't used that type of paper in decades since I used to get printouts from an IBM 1403 line printer. I sometimes wonder how people find these exploits. Would the features of SELinux be able to prevent taking advantage? I'm thinking the right SELinux rules would restrict what programs/processes could touch the password file.

[ChrisWalshZX]

Surely the kernel would use a sync lock to stop allowing these two threads from doing this? If what you are describing is correct (and I'm sure it is) then similar cases of COW and writing to the same memory page would occur quite frequently in the normal running of the OS and cause corruption? Thanks for the video.

[WolfireGaming]

When I first heard of Dirty COW, I was /really/ hoping it had something to do with cowsay. I was very disappointed.

[cashelfitzgibbons]

I love how I find this video the day I upgrade to ubuntu.

[SinanAkkoyun]

Numberphile and Computerphile can't cut the audio right...

[izimsi]

This one seems to have additional explanation, which was not present in the first upload.

[skelr]

Watching on a mac kept thinking I was getting emails lol

[Seegalgalguntijak]

These videos always start with "There's a new exploit been discovered for Linux", and that's just wrong, this exploit has been known for several years now!

[Winlith]

it's fixed in kernel versions 4.8.3, 4.7.9 and 4.4.26 LTS