[PATCH 1/2] perf/core: Bail out early if the request AUX area is out of bound

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

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 ]---

The pages for AUX area are organized as rb->aux_pages[] which alloced by
kcalloc_node() later. The kcalloc() family guarantees the pages are
physically contiguous (and virtually contiguous) with an order of
MAX_ORDER - 1 at maximum.

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>
---
 kernel/events/core.c                     | 10 ++++++++++
 tools/perf/Documentation/perf-record.txt |  3 ++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 435815d..83d4e29 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6404,6 +6404,16 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 			return -EINVAL;
 
 		nr_pages = vma_size / PAGE_SIZE;
+		/*
+		 * The pages for AUX area are organized as rb->aux_pages[]
+		 * which alloced by kcalloc_node() later. The kcalloc() family
+		 * guarantees the pages are physically contiguous (and
+		 * virtually contiguous) with an order of MAX_ORDER - 1 at
+		 * maximum MAX_ORDER. So bail out early if the request AUX area
+		 * is out of bound.
+		 */
+		if (get_order(nr_pages * sizeof(void *)) >= MAX_ORDER)
+			return -EINVAL;
 
 		mutex_lock(&event->mmap_mutex);
 		ret = -EINVAL;
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index ff815c2..a50a426 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -236,7 +236,8 @@ 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 11, the
+	maximum AUX area is limit to 2GB.
 
 -g::
 	Enables call-graph (stack chain/backtrace) recording for both
-- 
1.8.3.1