Re: [PATCH 12/12] Use down_read_unfair() for /sys/<pid>/exe and /sys/<pid>/maps files

From: David Howells
Date: Wed May 12 2010 - 09:12:03 EST


Michel Lespinasse <walken@xxxxxxxxxx> wrote:

> - Thread C is a monitoring process trying to read every /proc/pid/maps
> in the system. This requires acquiring the mmap_sem for read. Thread C
> blocks behind B, waiting for A to release the rwsem. If thread C
> could be allowed to run in parallel with A, it would probably get done
> long before thread A's disk access completes, thus not actually slowing
> down thread B.

Is it possible for someone to execute a DoS attack on another process using
a bunch of threads reading /proc/pid/maps?

David
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