> On 24-May-2022, at 4:53 PM, Vaibhav Jain <vaib...@linux.ibm.com> wrote: > > Sachin reported [1] that on a POWER-10 lpar he is seeing a kernel panic being > reported with vPMEM when papr_scm probe is being called. The panic is of the > form below and is observed only with following option disabled(profile) for > the > said LPAR 'Enable Performance Information Collection' in the HMC: > > Kernel attempted to write user page (1c) - exploit attempt? (uid: 0) > BUG: Kernel NULL pointer dereference on write at 0x0000001c > Faulting instruction address: 0xc008000001b90844 > Oops: Kernel access of bad area, sig: 11 [#1] > <snip> > NIP [c008000001b90844] drc_pmem_query_stats+0x5c/0x270 [papr_scm] > LR [c008000001b92794] papr_scm_probe+0x2ac/0x6ec [papr_scm] > Call Trace: > 0xc00000000941bca0 (unreliable) > papr_scm_probe+0x2ac/0x6ec [papr_scm] > platform_probe+0x98/0x150 > really_probe+0xfc/0x510 > __driver_probe_device+0x17c/0x230 > <snip> > ---[ end trace 0000000000000000 ]--- > Kernel panic - not syncing: Fatal exception > > On investigation looks like this panic was caused due to a 'stat_buffer' of > size==0 being provided to drc_pmem_query_stats() to fetch all performance > stats-ids of an NVDIMM. However drc_pmem_query_stats() shouldn't have been > called > since the vPMEM NVDIMM doesn't support and performance stat-id's. This was > caused > due to missing check for 'p->stat_buffer_len' at the beginning of > papr_scm_pmu_check_events() which indicates that the NVDIMM doesn't support > performance-stats. > > Fix this by introducing the check for 'p->stat_buffer_len' at the beginning of > papr_scm_pmu_check_events(). > > [1] > https://lore.kernel.org/all/6b3a522a-6a5f-4cc9-b268-0c63aa6e0...@linux.ibm.com > > Fixes: 0e0946e22f3665d2732 ("powerpc/papr_scm: Fix leaking nvdimm_events_map > elements") > Reported-by: Sachin Sant <sach...@linux.ibm.com> > Signed-off-by: Vaibhav Jain <vaib...@linux.ibm.com> > ---
Thanks Vaibhav for the patch. With the patch the reported problem is fixed. Tested-by: Sachin Sant <sach...@linux.ibm.com> -Sachin
