linux: riscv: set max_pfn to the PFN of the last page
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
Medium
|
Colin Ian King | ||
Focal |
Fix Released
|
Undecided
|
Unassigned |
Bug Description
== SRU Justification Focal/Groovy ==
The current max_pfn equals to zero. In this case, I found it caused users
cannot get some page information through /proc such as kpagecount in v5.6
kernel because of new sanity checks. The following message is displayed by
stress-ng test suite with the command "stress-ng --verbose --physpage 1 -t
1" on HiFive unleashed board.
# stress-ng --verbose --physpage 1 -t 1
stress-ng: debug: [109] 4 processors online, 4 processors configured
stress-ng: info: [109] dispatching hogs: 1 physpage
stress-ng: debug: [109] cache allocate: reducing cache level from L3 (too high) to L0
stress-ng: debug: [109] get_cpu_cache: invalid cache_level: 0
stress-ng: info: [109] cache allocate: using built-in defaults as no suitable cache found
stress-ng: debug: [109] cache allocate: default cache size: 2048K
stress-ng: debug: [109] starting stressors
stress-ng: debug: [109] 1 stressor spawned
stress-ng: debug: [110] stress-ng-physpage: started [110] (instance 0)
stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd34de000 in /proc/kpagecount, errno=0 (Success)
stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
...
stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
stress-ng: debug: [110] stress-ng-physpage: exited [110] (instance 0)
stress-ng: debug: [109] process [110] terminated
stress-ng: info: [109] successful run completed in 1.00s
#
== Fix ==
Upstream commit in linux-next:
commit c749bb2d554825e
Author: Vincent Chen <email address hidden>
Date: Mon Apr 27 14:59:24 2020 +0800
riscv: set max_pfn to the PFN of the last page
== Test Case ==
Without the patch, running stress-ng --verbose --physpage 1 -t
1 on HiFive unleashed board will trip the bug. With the patch, the test passes as follows:
# stress-ng --verbose --physpage 1 -t 1
stress-ng: debug: [104] 4 processors online, 4 processors configured stress-ng: info: [104] dispatching hogs: 1 physpage
stress-ng: info: [104] cache allocate: using defaults, can't determine cache details from sysfs
stress-ng: debug: [104] cache allocate: default cache size: 2048K
stress-ng: debug: [104] starting stressors
stress-ng: debug: [104] 1 stressor spawned
stress-ng: debug: [105] stress-ng-physpage: started [105] (instance 0) stress-ng: debug: [105] stress-ng-physpage: exited [105] (instance 0) stress-ng: debug: [104] process [105] terminated
stress-ng: info: [104] successful run completed in 1.01s
== Regression Potential ==
Small, this correctly fixes the max_pfn and max_low_pfn to the correct end of DRAM location. The fix now can be shown to set these appropriately because stress-ng no longer triggers this corner case.
CVE References
Changed in linux (Ubuntu): | |
importance: | Undecided → Medium |
assignee: | nobody → Colin Ian King (colin-king) |
status: | New → In Progress |
Changed in linux (Ubuntu Focal): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu): | |
status: | In Progress → Fix Released |
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- focal' to 'verification- done-focal' . If the problem still exists, change the tag 'verification- needed- focal' to 'verification- failed- focal'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.
See https:/ /wiki.ubuntu. com/Testing/ EnableProposed for documentation how to enable and use -proposed. Thank you!