** Also affects: linux (Ubuntu Groovy)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Groovy)
Importance: Undecided => High
** Changed in: linux (Ubuntu Groovy)
Status: New => In Progress
** Changed in: linux (Ubuntu Groovy)
Assignee: (unassigned) => Colin Ian King (colin-king)
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https://bugs.launchpad.net/bugs/1894613
Title:
risc-v 5.8 kernel oops on ftrace tests
Status in ubuntu-kernel-tests:
New
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Groovy:
In Progress
Bug description:
== SRU Groovy ==
Running the ftrace self tests results in null pointer dereference oops
on RISC-V and also on ARM64.
== Fix ==
Upstream commit
https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=4230e2deaa484b385aa01d598b2aea8e7f2660a6
== Testcase ==
Run the kernel ftrace selftest. Without the fix ftrace oopses on
RISC-V and ARM64 and can also hang on ARM64 too. With the fix, tests
run without oopsing or hanging.
== Regression Potential ==
This fix marks two functions as notrace, so the functionality of the
functions is not actually altered so the risk is negligible. If there
was a change in behaviour then RCU and stop machine operations will
break causing machine hangs. We don't observe this and RCU is used
heavily in the kernel so the code appears to not change the behaviour
as expected.
The only change is the the functions are no longer traceable via
ftrace, which is the desired operation.
-----------------
5.8.0-1-generic (buildd@riscv64-qemu-lcy01-015) (gcc (Ubuntu
10.2.0-5ubuntu2) 10.2.0, GNU ld (GNU Binutils for Ubuntu) 2.35)
#1-Ubuntu SMP Thu Aug 27 19:51:38 UTC 2020 (Ubuntu 5.8.0-1.1-generic
5.8.4
18:30:06 DEBUG| [stdout] # selftests: ftrace: ftracetest^M^M
18:30:07 DEBUG| [stdout] # === Ftrace unit tests ===^M^M
18:30:10 DEBUG| [stdout] # [1] Basic trace file check [PASS]^M^M
[17433.113458] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.113533] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.113552] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.113573] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.113591] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.114290] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.114306] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.114315] Oops [#1]^M^M
[17433.114630] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000^M^M
[17433.114690] Modules linked in: virtio_rng binfmt_misc uio_pdrv_genirq uio
drm sch_fq_codel drm_panel_orientation_quirks backlight ip_tables x_tables
autofs4 virtio_net net_failover virtio_blk failover [last unloaded:
signpost]^M^M
[17433.115296] CPU: 1 PID: 15 Comm: migration/1 Tainted: G W OE
5.8.0-1-generic #1-Ubuntu^M^M
[17433.115419] epc: 0000000000000000 ra : 0000000000000000 sp :
ffffffe1f5c67d90^M^M
[17433.115442] gp : ffffffe001722298 tp : ffffffe1f5c3ae00 t0 :
0000000000000000^M^M
[17433.115459] t1 : 0000000000006000 t2 : 00000000000bbc00 s0 :
0000000000000022^M^M
[17433.115475] s1 : ffffffe0002b7c12 a0 : ffffffe000963a64 a1 :
0000000000000022^M^M
[17433.115491] a2 : 0000000000000000 a3 : 0000000000000000 a4 :
0000000000000000^M^M
[17433.115507] a5 : ffffffe1fec95580 a6 : 00000000000000ff a7 :
0000000000000001^M^M
[17433.115523] s2 : 0000000000000001 s3 : ffffffe00009d580 s4 :
ffffffe001724210^M^M
[17433.115540] s5 : ffffffe1fec9a3b8 s6 : ffffffffffffffff s7 :
0000000000000001^M^M
[17433.115556] s8 : ffffffe0016f07cb s9 : ffffffe1e909bb80 s10:
ffffffe0002b7ba6^M^M
[17433.115573] s11: ffffffe1e909bba8 t3 : 000000000000006c t4 :
00000000002c73ba^M^M
[17433.115586] t5 : 00000000001f7fa8 t6 : ffffffe000c02d1c^M^M
[17433.115603] status: 0000000000000120 badaddr: 0000000000000000 cause:
000000000000000c^M^M
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