On 18/08/2015 20:05, Xavier Chantry wrote:
Package: src:linux
Version: 3.16.7-ckt11-1
Severity: important
Using Debian 3.16.7-ckt4-3 and a simple test case, we were able to reproduce a
kernel bug in msync system call.
The test case does the following:
1) create a 1MB file and mmap it
2) in a loop, select a 4k page in that file randomly, write with memset, then
run msync on that area in a thread
The problem was first seen in debian 3.12, and also reproduced with debian 3.16
and 4.1.0 kernels. Debian 3.2 was fine.
Vanilla kernels do not seem to be affected.
In fact the crash happens in vma_do_fput which comes with aufs4-mmap.patch
I confirm that the problem occurs on vanilla 4.1.6 after applying just
that patch :
./linux/debian/patches/features/all/aufs4/aufs4-mmap.patch from
svn://svn.debian.org/svn/kernel/dists/trunk
Same with the upstream patch at
https://raw.githubusercontent.com/sfjro/aufs4-standalone/aufs4.1/aufs4-mmap.patch
So I will report the problem to aufs-users at lists.sourceforge.net
Note that different call traces were seen by my colleagues (on different
debian kernels and machines), where the impact of aufs4 was less obvious
(it did not crash in vma_do_fput), I don't know what to make of it...
