From: Aboorva Devarajan <aboorvad@linux.ibm.com> mainline inclusion from mainline-v7.1-rc4 commit dbc30a57bd8e026995e9fa8e8c31cffd18542c01 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16017 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... ---------------------------------------------------------------------- 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 Signed-off-by: Luo Gengkun <luogengkun2@huawei.com> --- arch/powerpc/perf/hv-gpci.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/perf/hv-gpci.c b/arch/powerpc/perf/hv-gpci.c index 241551d1282f..0ec0bd311065 100644 --- a/arch/powerpc/perf/hv-gpci.c +++ b/arch/powerpc/perf/hv-gpci.c @@ -210,7 +210,7 @@ static ssize_t processor_bus_topology_show(struct device *dev, struct device_att 0, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; @@ -244,12 +244,14 @@ static ssize_t processor_bus_topology_show(struct device *dev, struct device_att starting_index, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; } +out_success: + put_cpu_var(hv_gpci_reqb); return n; out: @@ -278,7 +280,7 @@ static ssize_t processor_config_show(struct device *dev, struct device_attribute 0, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; @@ -312,12 +314,14 @@ static ssize_t processor_config_show(struct device *dev, struct device_attribute starting_index, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; } +out_success: + put_cpu_var(hv_gpci_reqb); return n; out: @@ -346,7 +350,7 @@ static ssize_t affinity_domain_via_virtual_processor_show(struct device *dev, 0, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; @@ -382,12 +386,14 @@ static ssize_t affinity_domain_via_virtual_processor_show(struct device *dev, starting_index, secondary_index, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; } +out_success: + put_cpu_var(hv_gpci_reqb); return n; out: @@ -416,7 +422,7 @@ static ssize_t affinity_domain_via_domain_show(struct device *dev, struct device 0, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; @@ -448,12 +454,14 @@ static ssize_t affinity_domain_via_domain_show(struct device *dev, struct device starting_index, 0, buf, &n, arg); if (!ret) - return n; + goto out_success; if (ret != H_PARAMETER) goto out; } +out_success: + put_cpu_var(hv_gpci_reqb); return n; out: -- 2.34.1