** Tags added: cscc
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https://bugs.launchpad.net/bugs/1799237
Title:
mprotect fails on ext4 with dax
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This bug was fixed in the package linux - 4.15.0-46.49
---
linux (4.15.0-46.49) bionic; urgency=medium
* linux: 4.15.0-46.49 -proposed tracker (LP: #1814726)
* mprotect fails on ext4 with dax (LP: #1799237)
- x86/speculation/l1tf: Exempt zeroed PTEs from inversion
*
I have not had a chance to try and reproduce the issue with the example
mentioned in this bug report but I have been able to verify that the
kernel in bionic-proposed fixes the problem I have reported in the
following bug report that has been rightfully marked as a duplicate:
This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
bionic' to 'verification-done-bionic'. If the problem still exists,
change the tag
Hi,
I have followed the steps from comment #27 and I was able to reproduce
the issue with bionic kernel 4.15.0-44-generic. I applied the suggested
fix (f19f5c49bbc3 x86/speculation/l1tf: Exempt zeroed PTEs from
inversion) and confirmed that it fixes the issue.
An SRU request has been sent with
** Changed in: linux (Ubuntu)
Status: Confirmed => Invalid
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Title:
mprotect fails on ext4 with dax
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I missed this report when I submitted my own report yesterday
(https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1813179). In my
case there is no workaround, so I am hoping this can be backported. It
is a one-line fix.
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** Changed in: linux (Ubuntu)
Assignee: Joseph Salisbury (jsalisbury) => (unassigned)
** Changed in: linux (Ubuntu Bionic)
Assignee: Joseph Salisbury (jsalisbury) => (unassigned)
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The problem is still present on kernel 4.15.0-43. Do you have any plans
to fix that?
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Title:
mprotect fails on ext4 with dax
To manage
I performed bisect on my own and it seems that following commit causes the
problem:
1920d4a1d4ff27ebfd34a99eca67c3c470c8c524 (x86/speculation/l1tf: Invert all not
present mappings).
In upstream kernel there is a commit fixing this:
f19f5c49bbc3ffcc9126cc245fc1b24cc29f4a37
The mprotect issue is
I started a kernel bisect between Ubuntu 4.15.0-20 and Ubuntu 4.15.0-34. The
kernel bisect will require testing of about 7-10 test kernels.
I built the first test kernel, up to the following commit:
9dcfef9fe59a2b4931f58b18fba731d00a4531bd
The test kernel can be downloaded from:
To summarize: 4.15.0-20 is the last kernel where mprotect works, all kernels
between 4.15.0-20 and 4.15.0-34 are not testable, 4.15.0-34 is the first kernel
that boots correctly and mprotect fails.
You have a test program, instructions how to run it and here's a guide how to
set up pmem
When I install kernel from package I have some problems with pmem
emulation and I can't really test this. Here is a simple script which
can be used to reproduce the problem (assuming you have pmem emulation,
e.g. using memmap and ndctl installed):
sudo umount /dev/pmem0
sudo ndctl
We can perform a kernel bisect, once we narrow down that last good
version and first bad one. Can you test 4.15.0-25? It can be
downloaded from:
https://launchpad.net/~canonical-kernel-
team/+archive/ubuntu/ppa/+build/15074499
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Eerything I described in previous comment was observed on Ubuntu kernel
(4.15.0-34). It worked fine on upstream and on ubuntu 4.15.0-20 so we
can still consider this a regression.
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Is this the case with all kernel versions, or can we still consider this
a regression in the kernel?
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Title:
mprotect fails on ext4 with dax
To
It turns out that this issue is only present for certain mapping lengths.
If I run the program, which I attached to the bug report, with size>=2M,
mprotect succeeds.
I have also tested this on device dax, and the results depend on alignment.
For 2M alignment, everything works fine, for 4k
I have tested the following upstream kernels and mprotect works fine on all of
them:
4.15.17-041517-generic
4.15.18-041518-generic
4.19.0-041900-generic
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I'd like to perform a bisect to figure out what commit caused this
regression. We need to identify the earliest kernel where the issue
started happening as well as the last kernel that did not have this
issue.
Can you test the following kernels and report back? Ubuntu 4.15.0-20 was
based on the
This bug was not present in the following kernel: 4.15.0-20-generic
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Title:
mprotect fails on ext4 with dax
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Did this issue start happening after an update/upgrade? Was there a
prior kernel version where you were not having this particular problem?
If it is a regression, we can perform a kernel bisect to narrow down
which commit introduced it.
Also, it might be good to test the latest mainline kernel
The latest mainline kernel is available from:
http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.19
Some documentation on it is here:
https://wiki.ubuntu.com/KernelMainlineBuilds
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Thanks. If the conclusion is that there's no action needed for pmdk, I
think the appropriate status for the pmdk task is Invalid - even though
pmdk use is affected. We wouldn't for example add a task for every
package if a kernel bug were to cause boot to fail, even though all
packages would be
This is purely kernel issue. It can be worked around in PMDK by code
change, as those mprotects are only safety precautions, but I really
wouldn't want to do this upstream.
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Is there something to be done in the user space pmdk component for this
bug, or is it purely a kernel issue?
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Title:
mprotect fails on ext4 with
Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: pmdk (Ubuntu)
Status: New => Confirmed
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Title:
** Description changed:
I have a file located on ext4 mounted with "dax". When I call mmap on that
file with protection flag different than PROT_NONE and pass the returned
address to mprotect(..., PROT_NONE) it fails with:
mprotect: Permission denied
This bug affects PMDK
** Also affects: pmdk (Ubuntu)
Importance: Undecided
Status: New
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Title:
mprotect fails on ext4 with dax
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Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: ubuntu
Status: New => Confirmed
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Title:
mprotect
apport information
** Tags added: apport-collected
** Description changed:
I have a file located on ext4 mounted with "dax". When I call mmap on that
file with protection flag different than PROT_NONE and pass the returned
address to mprotect(..., PROT_NONE) it fails with:
mprotect:
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
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Title:
mprotect fails on ext4 with dax
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** Description changed:
- I have a file located on ext4 mounted with "dax". When I call mmap on that
file with protection flag different than PROT_NONE
- and pass the returned address to mprotect(..., PROT_NONE) it fails with:
+ I have a file located on ext4 mounted with "dax". When I call mmap
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