Wednesday, February 27, 2013

Hotfix for leaking filedescriptors

I just came across this neat gdb trick. Say you have a badly written program that's leaking file descriptors all over.. and it's in prod (the horror!) and it's imperative that you let it limp along till the patched binary comes around... GDB can close the file descriptors for you!

Here's how:

Leaky Program

Lsof tells it all. Take note of the two open descriptors to /etc/passwd

Playing around with variables in GDB. Can you guess why we chose the magic value 2147483646? For a hint, look at the last gist in this post

What does lsof think?

Bulk close of fds

Shell output from leaky

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