Re: [Patch v2] perf/core: Bail out early if the request AUX area is out of bound

[Shuai Xue <xueshuai@linux.alibaba.com>]

On 2023/6/13 20:32, Shuai Xue wrote:
> When perf-record with a large AUX area, e.g 4GB, it fails with:
> 
>     #perf record -C 0 -m ,4G -e arm_spe_0// -- sleep 1
>     failed to mmap with 12 (Cannot allocate memory)
> 
> and it reveals a WARNING with __alloc_pages():
> 
> [   66.595604] ------------[ cut here ]------------
> [   66.600206] WARNING: CPU: 44 PID: 17573 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
> [   66.608375] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) aes_ce_blk(E) vfat(E) fat(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E)
> [   66.657719] CPU: 44 PID: 17573 Comm: perf Kdump: loaded Tainted: G            E      6.3.0-rc4+ #58
> [   66.666749] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
> [   66.674650] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> [   66.681597] pc : __alloc_pages+0x1ec/0x248
> [   66.685680] lr : __kmalloc_large_node+0xc0/0x1f8
> [   66.690285] sp : ffff800020523980
> [   66.693585] pmr_save: 000000e0
> [   66.696624] x29: ffff800020523980 x28: ffff000832975800 x27: 0000000000000000
> [   66.703746] x26: 0000000000100000 x25: 0000000000100000 x24: ffff8000083615d0
> [   66.710866] x23: 0000000000040dc0 x22: ffff000823d6d140 x21: 000000000000000b
> [   66.717987] x20: 000000000000000b x19: 0000000000000000 x18: 0000000000000030
> [   66.725108] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff000823d6d6d0
> [   66.732229] x14: 0000000000000000 x13: 343373656761705f x12: 726e202c30206574
> [   66.739350] x11: 00000000ffff7fff x10: 00000000ffff7fff x9 : ffff8000083af570
> [   66.746471] x8 : 00000000000bffe8 x7 : c0000000ffff7fff x6 : 000000000005fff4
> [   66.753592] x5 : 0000000000000000 x4 : ffff000823d6d8d8 x3 : 0000000000000000
> [   66.760713] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000040dc0
> [   66.767834] Call trace:
> [   66.770267]  __alloc_pages+0x1ec/0x248
> [   66.774003]  __kmalloc_large_node+0xc0/0x1f8
> [   66.778259]  __kmalloc_node+0x134/0x1e8
> [   66.782081]  rb_alloc_aux+0xe0/0x298
> [   66.785643]  perf_mmap+0x440/0x660
> [   66.789031]  mmap_region+0x308/0x8a8
> [   66.792593]  do_mmap+0x3c0/0x528
> [   66.795807]  vm_mmap_pgoff+0xf4/0x1b8
> [   66.799456]  ksys_mmap_pgoff+0x18c/0x218
> [   66.803365]  __arm64_sys_mmap+0x38/0x58
> [   66.807187]  invoke_syscall+0x50/0x128
> [   66.810922]  el0_svc_common.constprop.0+0x58/0x188
> [   66.815698]  do_el0_svc+0x34/0x50
> [   66.818999]  el0_svc+0x34/0x108
> [   66.822127]  el0t_64_sync_handler+0xb8/0xc0
> [   66.826296]  el0t_64_sync+0x1a4/0x1a8
> [   66.829946] ---[ end trace 0000000000000000 ]---
> 
> 'rb->aux_pages' allocated by kcalloc() is a pointer array which is used to
> maintains AUX trace pages. The allocated page for this array is physically
> contiguous (and virtually contiguous) with an order of 0..MAX_ORDER. If the
> size of pointer array crosses the limitation set by MAX_ORDER, it reveals a
> WARNING.
> 
> So bail out early with -EINVAL if the request AUX area is out of bound,
> e.g.:
> 
>     #perf record -C 0 -m ,4G -e arm_spe_0// -- sleep 1
>     failed to mmap with 22 (Invalid argument)
> 
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> ---
> changes since v1:
> - drop out patch2 because it has been fixed on upstream (Thanks James for reminding)
> - move sanity check into rb_alloc_aux (per Leo)
> - add overflow check (per James)


Hi, all,

Gentle Ping.

Best Regards,
Shuai

> ---
>  kernel/events/ring_buffer.c              | 13 +++++++++++++
>  tools/perf/Documentation/perf-record.txt |  3 ++-
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index a0433f37b024..e514aaba9d42 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -673,6 +673,7 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event,
>  	bool overwrite = !(flags & RING_BUFFER_WRITABLE);
>  	int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
>  	int ret = -ENOMEM, max_order;
> +	size_t bytes;
>  
>  	if (!has_aux(event))
>  		return -EOPNOTSUPP;
> @@ -699,6 +700,18 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event,
>  		watermark = 0;
>  	}
>  
> +	/*
> +	 * 'rb->aux_pages' allocated by kcalloc() is a pointer array which is
> +	 * used to maintains AUX trace pages. The allocated page for this array
> +	 * is physically contiguous (and virtually contiguous) with an order of
> +	 * 0..MAX_ORDER. If the size of pointer array crosses the limitation set
> +	 * by MAX_ORDER, it reveals a WARNING.
> +	 *
> +	 * So bail out early if the request AUX area is out of bound.
> +	 */
> +	if (check_mul_overflow(nr_pages, sizeof(void *), &bytes) ||
> +	    get_order(bytes) > MAX_ORDER)
> +		return -EINVAL;
>  	rb->aux_pages = kcalloc_node(nr_pages, sizeof(void *), GFP_KERNEL,
>  				     node);
>  	if (!rb->aux_pages)
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 680396c56bd1..5d8d3ad084ed 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -290,7 +290,8 @@ OPTIONS
>  	specification with appended unit character - B/K/M/G. The
>  	size is rounded up to have nearest pages power of two value.
>  	Also, by adding a comma, the number of mmap pages for AUX
> -	area tracing can be specified.
> +	area tracing can be specified. With MAX_ORDER set as 10 on
> +	arm64 platform , the maximum AUX area is limited to 2GiB.
>  
>  -g::
>  	Enables call-graph (stack chain/backtrace) recording for both