Re: [PATCH 1/2] arm64: mm: drop VM_FAULT_BADMAP/VM_FAULT_BADACCESS

Kefeng Wang
2024-04-10T11:54:01Z

On 2024/4/10 19:24, Aishwarya TCV wrote:
>
>
> On 07/04/2024 09:12, Kefeng Wang wrote:
>> If bad map or access, directly set si_code to SEGV_MAPRR or SEGV_ACCERR,
>> also set fault to 0 and goto error handling, which make us to drop the
>> arch's special vm fault reason.
>>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>> arch/arm64/mm/fault.c | 41 ++++++++++++++++++-----------------------
>> 1 file changed, 18 insertions(+), 23 deletions(-)
>
> Hi Kefeng,
>
> While running LTP test suite, I observed that few test cases are unable
> to kill exe when run against next-master(next-20240409) kernel with
> Arm64 on JUNO in our CI. I can send the full logs if required, but it
> doesn't say much.

Sorry about it, as Catalin pointed, there is issue in this patch, and
I replied today, could you help to test with following changes, many thanks.

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 61a2acae0dca..451ba7cbd5ad 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -604,6 +604,7 @@ static int __kprobes do_page_fault(unsigned long
far, unsigned long esr,
}

if (!(vma->vm_flags & vm_flags)) {
+ mmap_read_unlock(mm);
fault = 0;
si_code = SEGV_ACCERR;
goto bad_area;
@@ -632,6 +633,7 @@ static int __kprobes do_page_fault(unsigned long
far, unsigned long esr,
if (likely(!(fault & VM_FAULT_ERROR)))
return 0;

+ si_code = SEGV_MAPERR;
bad_area:
/*
* If we are in kernel mode at this point, we have no context to

>
> A bisect identified cf0049a15207a5a78798105eff789c2025bcf652 as the
> first bad commit. Bisected it on the tag "next-20240409" at repo
> "https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git".
>
> This works fine on Linux version v6.9-rc3
>
> Here are some of the failing test cases in LTP quickhit:
> -----------------------------
> chdir01
> link04
> select03
> unlink07
>
>
> Failure log:
> -----------
> 06:06:49.288908 Test timeouted, sending SIGKILL!
> 06:06:54.293806 Test timeouted, sending SIGKILL!
> 06:06:59.296872 Test timeouted, sending SIGKILL!
> 06:07:04.292044 Test timeouted, sending SIGKILL!
> 06:07:09.290185 Test timeouted, sending SIGKILL!
> 06:07:14.295134 Test timeouted, sending SIGKILL!
> 06:07:19.293279 Test timeouted, sending SIGKILL!
> 06:07:24.292405 Test timeouted, sending SIGKILL!
> 06:07:24.292790 Cannot kill test processes!
> 06:07:24.296564 Congratulation, likely test hit a kernel bug.
> 06:07:24.301315 Exiting uncleanly...
>
>
> Bisect log:
> ----------
> git bisect start
> # good: [fec50db7033ea478773b159e0e2efb135270e3b7] Linux 6.9-rc3
> git bisect good fec50db7033ea478773b159e0e2efb135270e3b7
> # bad: [a053fd3ca5d1b927a8655f239c84b0d790218fda] Add linux-next
> specific files for 20240409
> git bisect bad a053fd3ca5d1b927a8655f239c84b0d790218fda
> # bad: [4eb0063b031ea720cd8971e3e3d2426d27c5d7a6] Merge branch
> 'mtd/next' of git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git
> git bisect bad 4eb0063b031ea720cd8971e3e3d2426d27c5d7a6
> # bad: [24dde11bfadd5f38c6cca3cea6f16971bd10dc86] Merge branch
> 'for-next' of git://github.com/Xilinx/linux-xlnx.git
> git bisect bad 24dde11bfadd5f38c6cca3cea6f16971bd10dc86
> # bad: [bef23348d7e75c502399ba1a24627aa447b816dc] Merge branch
> 'mm-everything' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> git bisect bad bef23348d7e75c502399ba1a24627aa447b816dc
> # good: [3317f7faabc24b500c26d02615ac75ca2786e272] mm: swap:
> free_swap_and_cache_nr() as batched free_swap_and_cache()
> git bisect good 3317f7faabc24b500c26d02615ac75ca2786e272
> # good: [541970e62546ff5c96622669f2796d43b1a406e3] Merge branch
> 'gpio/for-current' of
> git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git
> git bisect good 541970e62546ff5c96622669f2796d43b1a406e3
> # bad: [1df265717e0f9d96079073189f6e6c52a48e493c]
> __mod_memcg_lruvec_state-enhance-diagnostics-fix
> git bisect bad 1df265717e0f9d96079073189f6e6c52a48e493c
> # bad: [19ab4054346474c2b456f9bff6a98e41e5e46224] hugetlb: Simplify
> hugetlb_wp() arguments
> git bisect bad 19ab4054346474c2b456f9bff6a98e41e5e46224
> # good: [75ef450aa9828ca20817c46c5b99f131156f6eee] x86: mm: accelerate
> pagefault when badaccess
> git bisect good 75ef450aa9828ca20817c46c5b99f131156f6eee
> # bad: [c6b5a19e679bb713efd57d82f9080f780e0bb60a] mm/treewide: rename
> CONFIG_HAVE_FAST_GUP to CONFIG_HAVE_GUP_FAST
> git bisect bad c6b5a19e679bb713efd57d82f9080f780e0bb60a
> # bad: [01446d1e9e627945664f2a1daa53e8720946d0cd] mm: remove struct page
> from get_shadow_from_swap_cache
> git bisect bad 01446d1e9e627945664f2a1daa53e8720946d0cd
> # bad: [8f9d6a30dd992c44debea3161083a6c2cd3ad87f] arm: mm: drop
> VM_FAULT_BADMAP/VM_FAULT_BADACCESS
> git bisect bad 8f9d6a30dd992c44debea3161083a6c2cd3ad87f
> # bad: [cf0049a15207a5a78798105eff789c2025bcf652] arm64: mm: drop
> VM_FAULT_BADMAP/VM_FAULT_BADACCESS
> git bisect bad cf0049a15207a5a78798105eff789c2025bcf652
> # first bad commit: [cf0049a15207a5a78798105eff789c2025bcf652] arm64:
> mm: drop VM_FAULT_BADMAP/VM_FAULT_BADACCESSgit bisect log
>
>
> Thanks,
> Aishwarya