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| author | Aboorva Devarajan <aboorvad@linux.ibm.com> | 2026-05-08 09:42:56 +0530 |
|---|---|---|
| committer | Madhavan Srinivasan <maddy@linux.ibm.com> | 2026-05-12 11:51:17 +0530 |
| commit | dbc30a57bd8e026995e9fa8e8c31cffd18542c01 (patch) | |
| tree | 3a2f123d37e469eed6b862eed6f8e14115e70397 /tools/perf/scripts/python/bin/stackcollapse-report | |
| parent | aef656a0e6c01796190bb5bd2bdba1c644ed7811 (diff) | |
| download | linux-dbc30a57bd8e026995e9fa8e8c31cffd18542c01.tar.gz linux-dbc30a57bd8e026995e9fa8e8c31cffd18542c01.zip | |
powerpc/hv-gpci: fix preempt count leak in sysfs show paths
Four sysfs show() callbacks in hv-gpci take get_cpu_var(hv_gpci_reqb)
(which calls preempt_disable()) but only call the matching put_cpu_var()
on the error path under the 'out:' label. Every successful read leaks
one preempt_disable():
processor_bus_topology_show()
processor_config_show()
affinity_domain_via_virtual_processor_show()
affinity_domain_via_domain_show()
(affinity_domain_via_partition_show() was already correct.)
On a CONFIG_PREEMPT=y kernel, repeated reads raise preempt_count and
eventually return to userspace with preemption still disabled. The
next user-mode page fault then hits faulthandler_disabled() == 1,
gets forced to SIGSEGV, and the resulting coredump trips
'BUG: scheduling while atomic' in call_usermodehelper_exec ->
wait_for_completion_state -> schedule:
BUG: scheduling while atomic: <task>/<pid>/0x00000004
...
__schedule_bug+0x6c/0x90
__schedule+0x58c/0x13a0
schedule+0x48/0x1a0
schedule_timeout+0x104/0x170
wait_for_completion_state+0x16c/0x330
call_usermodehelper_exec+0x254/0x2d0
vfs_coredump+0x1050/0x2590
get_signal+0xb9c/0xc80
do_notify_resume+0xf8/0x470
Add an out_success label that calls put_cpu_var() before returning
the byte count, mirroring affinity_domain_via_partition_show().
Fixes: 71f1c39647d8 ("powerpc/hv_gpci: Add sysfs file inside hv_gpci device to show processor bus topology information")
Fixes: 1a160c2a13c6 ("powerpc/hv_gpci: Add sysfs file inside hv_gpci device to show processor config information")
Fixes: 71a7ccb478fc ("powerpc/hv_gpci: Add sysfs file inside hv_gpci device to show affinity domain via virtual processor information")
Fixes: a69a57cac1ec ("powerpc/hv_gpci: Add sysfs file inside hv_gpci device to show affinity domain via domain information")
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260508041256.3447113-1-aboorvad@linux.ibm.com
Diffstat (limited to 'tools/perf/scripts/python/bin/stackcollapse-report')
0 files changed, 0 insertions, 0 deletions