linux-kernel - Re: [PATCH] sched/numa: Fix the potential null pointer dereference in task_numa

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <rackpsb5traqwwyqirfo7r5k66m73k7n7nxvyhz53v77gprqy3@zzj7dayxltl3>
Date: Fri, 25 Oct 2024 09:38:28 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Shawn Wang <shawnwang@...ux.alibaba.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, baolin.wang@...ux.alibaba.com,
        mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        vschneid@...hat.com
Subject: Re: [PATCH] sched/numa: Fix the potential null pointer dereference
 in task_numa_work()

* Shawn Wang <shawnwang@...ux.alibaba.com> [241024 22:22]:
> When running stress-ng-vm-segv test, we found a null pointer dereference
> error in task_numa_work(). Here is the backtrace:
> 
>   [323676.066985] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
>   ......
>   [323676.067108] CPU: 35 PID: 2694524 Comm: stress-ng-vm-se
>   ......
>   [323676.067113] pstate: 23401009 (nzCv daif +PAN -UAO +TCO +DIT +SSBS BTYPE=--)
>   [323676.067115] pc : vma_migratable+0x1c/0xd0
>   [323676.067122] lr : task_numa_work+0x1ec/0x4e0
>   [323676.067127] sp : ffff8000ada73d20
>   [323676.067128] x29: ffff8000ada73d20 x28: 0000000000000000 x27: 000000003e89f010
>   [323676.067130] x26: 0000000000080000 x25: ffff800081b5c0d8 x24: ffff800081b27000
>   [323676.067133] x23: 0000000000010000 x22: 0000000104d18cc0 x21: ffff0009f7158000
>   [323676.067135] x20: 0000000000000000 x19: 0000000000000000 x18: ffff8000ada73db8
>   [323676.067138] x17: 0001400000000000 x16: ffff800080df40b0 x15: 0000000000000035
>   [323676.067140] x14: ffff8000ada73cc8 x13: 1fffe0017cc72001 x12: ffff8000ada73cc8
>   [323676.067142] x11: ffff80008001160c x10: ffff000be639000c x9 : ffff8000800f4ba4
>   [323676.067145] x8 : ffff000810375000 x7 : ffff8000ada73974 x6 : 0000000000000001
>   [323676.067147] x5 : 0068000b33e26707 x4 : 0000000000000001 x3 : ffff0009f7158000
>   [323676.067149] x2 : 0000000000000041 x1 : 0000000000004400 x0 : 0000000000000000
>   [323676.067152] Call trace:
>   [323676.067153]  vma_migratable+0x1c/0xd0
>   [323676.067155]  task_numa_work+0x1ec/0x4e0
>   [323676.067157]  task_work_run+0x78/0xd8
>   [323676.067161]  do_notify_resume+0x1ec/0x290
>   [323676.067163]  el0_svc+0x150/0x160
>   [323676.067167]  el0t_64_sync_handler+0xf8/0x128
>   [323676.067170]  el0t_64_sync+0x17c/0x180
>   [323676.067173] Code: d2888001 910003fd f9000bf3 aa0003f3 (f9401000)
>   [323676.067177] SMP: stopping secondary CPUs
>   [323676.070184] Starting crashdump kernel...
> 
> stress-ng-vm-segv in stress-ng is used to stress test the SIGSEGV error
> handling function of the system, which tries to cause a SIGSEGV error on
> return from unmapping the whole address space of the child process.
> 
> Normally this program will not cause kernel crashes. But before the
> munmap system call returns to user mode, a potential task_numa_work()
> for numa balancing could be added and executed. In this scenario, since the
> child process has no vma after munmap, the vma_next() in task_numa_work()
> will return a null pointer even if the vma iterator restarts from 0.
> 
> Recheck the vma pointer before dereferencing it in task_numa_work().
> 
> Fixes: 214dbc428137 ("sched: convert to vma iterator")
> Cc: stable@...r.kernel.org # v6.2+
> Signed-off-by: Shawn Wang <shawnwang@...ux.alibaba.com>

Reviewed-by:  Liam R. Howlett <Liam.Howlett@...cle.com>

> ---
>  kernel/sched/fair.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c157d4860a3b..b4c3277cd563 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3369,7 +3369,7 @@ static void task_numa_work(struct callback_head *work)
>  		vma = vma_next(&vmi);
>  	}
>  
> -	do {
> +	for (; vma; vma = vma_next(&vmi)) {
>  		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
>  			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
>  			trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_UNSUITABLE);
> @@ -3491,7 +3491,7 @@ static void task_numa_work(struct callback_head *work)
>  		 */
>  		if (vma_pids_forced)
>  			break;
> -	} for_each_vma(vmi, vma);
> +	}
>  
>  	/*
>  	 * If no VMAs are remaining and VMAs were skipped due to the PID
> -- 
> 2.43.5
> 
>