Regression on drm-tip

Wed Jan 31 05:34:53 UTC 2024

Hello Richard,

Hope you are doing well. I am Chaitanya from the Linux graphics team in Intel.

This mail is regarding a regression we are seeing in our CI runs[1] on drm-tip[2] repository.
These are captured by gitlab issues[3].

We bisected the issue and have found the following commit to be the first bad commit.
`````````````````````````````````````````````````````````````````````````````````````````````````````````
commit a0b84213f947176ddcd0e96e0751a109f28cde21
Author: Richard Fitzgerald rf at opensource.cirrus.com
Date:   Mon Dec 18 15:17:29 2023 +0000

    kunit: Fix NULL-dereference in kunit_init_suite() if suite->log is NULL

    suite->log must be checked for NULL before passing it to
    string_stream_clear(). This was done in kunit_init_test() but was missing
    from kunit_init_suite().

    Signed-off-by: Richard Fitzgerald rf at opensource.cirrus.com
    Fixes: 6d696c4695c5 ("kunit: add ability to run tests after boot using debugfs")
    Reviewed-by: Rae Moar rmoar at google.com
    Acked-by: David Gow davidgow at google.com
    Reviewed-by: Muhammad Usama Anjum usama.anjum at collabora.com
    Signed-off-by: Shuah Khan skhan at linuxfoundation.org

lib/kunit/test.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
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We tried reverting the patch and the original issue is not seen but it results in NULL pointer deference[4] which I am guessing is expected.

Could you please check why the patch causes this regression and provide a fix if necessary?

[1] https://intel-gfx-ci.01.org/tree/drm-tip/index.html?testfilter=drm
[2] https://cgit.freedesktop.org/drm-tip/
[3] https://gitlab.freedesktop.org/drm/intel/-/issues/10140
      https://gitlab.freedesktop.org/drm/intel/-/issues/10143
[4]
	[  179.849411] [IGT] drm_buddy: executing
	[  179.856385] [IGT] drm_buddy: starting subtest drm_buddy
	[  179.862594] KTAP version 1
	[  179.862600] 1..1
	[  179.863375] BUG: kernel NULL pointer dereference, address: 0000000000000030
	[  179.863381] #PF: supervisor read access in kernel mode
	[  179.863384] #PF: error_code(0x0000) - not-present page
	[  179.863387] PGD 0 P4D 0
	[  179.863391] Oops: 0000 [#1] PREEMPT SMP NOPTI
	[  179.863395] CPU: 1 PID: 1319 Comm: drm_buddy Not tainted 6.8.0-rc1-bisecttrail015 #16
	[  179.863398] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P DDR5 SODIMM SBS RVP, BIOS MTLPFWI1.R00.3471.D81.2311291340 11/29/2023
	[  179.863400] RIP: 0010:__lock_acquire+0x71f/0x2300
	[  179.863408] Code: 84 03 06 00 00 44 8b 15 27 f6 72 01 45 85 d2 0f 84 9c 00 00 00 f6 45 22 10 0f 84 63 03 00 00 41 bf 01 00 00 00 e9 8a 00 00 00 <48> 81 3f 40 d7 fa 82 41 b9 00 00 00 00 45 0f 	45 c8 83 fe 01 0f 87
	...
	[  179.863445] PKRU: 55555554
	[  179.863448] Call Trace:
	[  179.863450]  <TASK>
	[  179.863453]  ? __die_body+0x1a/0x60
	[  179.863459]  ? page_fault_oops+0x156/0x450
	[  179.863465]  ? do_user_addr_fault+0x65/0x9e0
	[  179.863472]  ? exc_page_fault+0x68/0x1a0
	[  179.863479]  ? asm_exc_page_fault+0x26/0x30
	[  179.863487]  ? __lock_acquire+0x71f/0x2300
	[  179.863493]  ? __pfx_do_sync_core+0x10/0x10
	[  179.863500]  lock_acquire+0xd8/0x2d0
	[  179.863505]  ? string_stream_clear+0x29/0xb0 [kunit]
	[  179.863523]  _raw_spin_lock+0x2e/0x40
	[  179.863528]  ? string_stream_clear+0x29/0xb0 [kunit]
	[  179.863540]  string_stream_clear+0x29/0xb0 [kunit]
	[  179.863554]  __kunit_test_suites_init+0x7e/0xe0 [kunit]
	[  179.863568]  kunit_module_notify+0x20f/0x220 [kunit]
	[  179.863583]  notifier_call_chain+0x46/0x130
	[  179.863591]  notifier_call_chain_robust+0x3e/0x90
	[  179.863598]  blocking_notifier_call_chain_robust+0x42/0x60
	[  179.863605]  load_module+0x1bcd/0x1f80
	[  179.863617]  ? init_module_from_file+0x86/0xd0
	[  179.863621]  init_module_from_file+0x86/0xd0
	[  179.863629]  idempotent_init_module+0x17c/0x230
	[  179.863637]  __x64_sys_finit_module+0x56/0xb0
	[  179.863642]  do_syscall_64+0x6f/0x140
	[  179.863649]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
	[  179.863654] RIP: 0033:0x7f0e6676195d