kernel null pointer at nvme_tcp_init_iter+0x7d/0xd0 [nvme_tcp]

[Sagi Grimberg]

> Hi Sagi
> 
> On 2/8/21 5:46 PM, Sagi Grimberg wrote:
>>
>>> Hello
>>>
>>> We found this kernel NULL pointer issue with latest 
>>> linux-block/for-next and it's 100% reproduced, let me know if you 
>>> need more info/testing, thanks
>>>
>>> Kernel repo: 
>>> https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git
>>> Commit: 11f8b6fd0db9 - Merge branch 'for-5.12/io_uring' into for-next
>>>
>>> Reproducer: blktests nvme-tcp/012
>>
>> Thanks for reporting Ming, I've tried to reproduce this on my VM
>> but did not succeed. Given that you have it 100% reproducible,
>> can you try to revert commit:
>>
>> 0dc9edaf80ea nvme-tcp: pass multipage bvec to request iov_iter
>>
> 
> Revert this commit fixed the issue and I've attached the config. :)

Good to know,

I see some differences that I should probably change to hit this:
--
@@ -254,14 +256,15 @@ CONFIG_PERF_EVENTS=y
  # end of Kernel Performance Events And Counters

  CONFIG_VM_EVENT_COUNTERS=y
+CONFIG_SLUB_DEBUG=y
  # CONFIG_COMPAT_BRK is not set
-CONFIG_SLAB=y
-# CONFIG_SLUB is not set
-# CONFIG_SLOB is not set
-CONFIG_SLAB_MERGE_DEFAULT=y
-# CONFIG_SLAB_FREELIST_RANDOM is not set
+# CONFIG_SLAB is not set
+CONFIG_SLUB=y
+# CONFIG_SLAB_MERGE_DEFAULT is not set
+CONFIG_SLAB_FREELIST_RANDOM=y
  # CONFIG_SLAB_FREELIST_HARDENED is not set
-# CONFIG_SHUFFLE_PAGE_ALLOCATOR is not set
+CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
+CONFIG_SLUB_CPU_PARTIAL=y
  CONFIG_SYSTEM_DATA_VERIFICATION=y
  CONFIG_PROFILING=y
  CONFIG_TRACEPOINTS=y
@@ -299,7 +302,8 @@ CONFIG_HAVE_INTEL_TXT=y
  CONFIG_X86_64_SMP=y
  CONFIG_ARCH_SUPPORTS_UPROBES=y
  CONFIG_FIX_EARLYCON_MEM=y
-CONFIG_PGTABLE_LEVELS=4
+CONFIG_DYNAMIC_PHYSICAL_MASK=y
+CONFIG_PGTABLE_LEVELS=5
  CONFIG_CC_HAS_SANE_STACKPROTECTOR=y
--

Probably CONFIG_SLUB and CONFIG_SLUB_DEBUG should be used.