Question on page length clamping in hash walk fix and syscall crashes
From: Xavier Roche
Date: Thu Jul 28 2016 - 06:07:23 EST
We stumble upon an issue while using an AF_ALG socket to compute a hash
(crc32) directly in the kernel (using splice magic)
The issue has been fixed AFAICS by Herbert Xu in
cc440a5b68873b7b98c3130d09a69a1b13acb0b7 in a rather isolated patch (three
I could validate that the patch does indeed fix the issue we were having.
This bug seems to be more than a computation issue, as we experienced
weird crashes in random syscall when it is triggered (ie. unpatched),
such as fork, or futex-related primitives (!).
The issue can be reproduced with this standalone program:
Most up-to-date stable distro are using the buggy version (Centos 7:
3.10.0, Ubuntu trusty: 3.13.0, Fedora 22: 4.3.6, etc.)
Question: is the weird behavior observed (crashes inside kernel)
"normal" w.r.t this issue, and how cherry-pick policy is organized w.r.t
older kernel releases (LTS only ?)
[ Typically the bug does not appear in 3.14.70, 3.16.0, 3.19.0 or 4.2.0 ]
And sorry in advance if this question has already been answered, but I
could not find any clear hint.