Message-ID: <20250314195619.23772-2-enjuk@amazon.com>
Date: Sat, 15 Mar 2025 04:54:24 +0900
From: Kohei Enju <enjuk@...zon.com>
To: <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
	<daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, "Andrii
 Nakryiko" <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>,
	"Eduard Zingerman" <eddyz87@...il.com>, Song Liu <song@...nel.org>, Yonghong
 Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, Stanislav
 Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
	<jolsa@...nel.org>, Peilin Ye <yepeilin@...gle.com>, Ilya Leoshkevich
	<iii@...ux.ibm.com>, Kuniyuki Iwashima <kuniyu@...zon.com>,
	<kohei.enju@...il.com>, Kohei Enju <enjuk@...zon.com>,
	<syzbot+a5964227adc0f904549c@...kaller.appspotmail.com>
Subject: [PATCH bpf-next v1] bpf: Fix out-of-bounds read in check_atomic_load/store()

syzbot reported the following splat [0].

In check_atomic_load/store(), register validity is not checked before
atomic_ptr_type_ok(). This causes the out-of-bounds read in is_ctx_reg()
called from atomic_ptr_type_ok() when the register number is MAX_BPF_REG
or greater.

Add check_reg_arg() before atomic_ptr_type_ok(), and return early when
the register is invalid.

[0]
 BUG: KASAN: slab-out-of-bounds in is_ctx_reg kernel/bpf/verifier.c:6185 [inline]
 BUG: KASAN: slab-out-of-bounds in atomic_ptr_type_ok+0x3d7/0x550 kernel/bpf/verifier.c:6223
 Read of size 4 at addr ffff888141b0d690 by task syz-executor143/5842

 CPU: 1 UID: 0 PID: 5842 Comm: syz-executor143 Not tainted 6.14.0-rc3-syzkaller-gf28214603dc6 #0
 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
 Call Trace:
  <TASK>
  __dump_stack lib/dump_stack.c:94 [inline]
  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
  print_address_description mm/kasan/report.c:408 [inline]
  print_report+0x16e/0x5b0 mm/kasan/report.c:521
  kasan_report+0x143/0x180 mm/kasan/report.c:634
  is_ctx_reg kernel/bpf/verifier.c:6185 [inline]
  atomic_ptr_type_ok+0x3d7/0x550 kernel/bpf/verifier.c:6223
  check_atomic_store kernel/bpf/verifier.c:7804 [inline]
  check_atomic kernel/bpf/verifier.c:7841 [inline]
  do_check+0x89dd/0xedd0 kernel/bpf/verifier.c:19334
  do_check_common+0x1678/0x2080 kernel/bpf/verifier.c:22600
  do_check_main kernel/bpf/verifier.c:22691 [inline]
  bpf_check+0x165c8/0x1cca0 kernel/bpf/verifier.c:23821
  bpf_prog_load+0x1664/0x20e0 kernel/bpf/syscall.c:2967
  __sys_bpf+0x4ea/0x820 kernel/bpf/syscall.c:5811
  __do_sys_bpf kernel/bpf/syscall.c:5918 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:5916 [inline]
  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5916
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
 RIP: 0033:0x7fa3ac86bab9
 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
 RSP: 002b:00007ffe50fff5f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa3ac86bab9
 RDX: 0000000000000094 RSI: 00004000000009c0 RDI: 0000000000000005
 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000006
 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
 R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
  </TASK>

 Allocated by task 5842:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
  __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
  kasan_kmalloc include/linux/kasan.h:260 [inline]
  __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4325
  kmalloc_noprof include/linux/slab.h:901 [inline]
  kzalloc_noprof include/linux/slab.h:1037 [inline]
  do_check_common+0x1ec/0x2080 kernel/bpf/verifier.c:22499
  do_check_main kernel/bpf/verifier.c:22691 [inline]
  bpf_check+0x165c8/0x1cca0 kernel/bpf/verifier.c:23821
  bpf_prog_load+0x1664/0x20e0 kernel/bpf/syscall.c:2967
  __sys_bpf+0x4ea/0x820 kernel/bpf/syscall.c:5811
  __do_sys_bpf kernel/bpf/syscall.c:5918 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:5916 [inline]
  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5916
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

 The buggy address belongs to the object at ffff888141b0d000
  which belongs to the cache kmalloc-2k of size 2048
 The buggy address is located 312 bytes to the right of
  allocated 1368-byte region [ffff888141b0d000, ffff888141b0d558)

 The buggy address belongs to the physical page:
 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x141b08
 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
 flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
 page_type: f5(slab)
 raw: 057ff00000000040 ffff88801b042000 dead000000000100 dead000000000122
 raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
 head: 057ff00000000040 ffff88801b042000 dead000000000100 dead000000000122
 head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
 head: 057ff00000000003 ffffea000506c201 ffffffffffffffff 0000000000000000
 head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
 page dumped because: kasan: bad access detected
 page_owner tracks the page as allocated
 page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 8909973200, free_ts 0
  set_page_owner include/linux/page_owner.h:32 [inline]
  post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1585
  prep_new_page mm/page_alloc.c:1593 [inline]
  get_page_from_freelist+0x3a8c/0x3c20 mm/page_alloc.c:3538
  __alloc_frozen_pages_noprof+0x264/0x580 mm/page_alloc.c:4805
  alloc_pages_mpol+0x311/0x660 mm/mempolicy.c:2270
  alloc_slab_page mm/slub.c:2423 [inline]
  allocate_slab+0x8f/0x3a0 mm/slub.c:2587
  new_slab mm/slub.c:2640 [inline]
  ___slab_alloc+0xc27/0x14a0 mm/slub.c:3826
  __slab_alloc+0x58/0xa0 mm/slub.c:3916
  __slab_alloc_node mm/slub.c:3991 [inline]
  slab_alloc_node mm/slub.c:4152 [inline]
  __kmalloc_cache_noprof+0x27b/0x390 mm/slub.c:4320
  kmalloc_noprof include/linux/slab.h:901 [inline]
  kzalloc_noprof include/linux/slab.h:1037 [inline]
  virtio_pci_probe+0x54/0x340 drivers/virtio/virtio_pci_common.c:689
  local_pci_probe drivers/pci/pci-driver.c:324 [inline]
  pci_call_probe drivers/pci/pci-driver.c:392 [inline]
  __pci_device_probe drivers/pci/pci-driver.c:417 [inline]
  pci_device_probe+0x6c5/0xa10 drivers/pci/pci-driver.c:451
  really_probe+0x2b9/0xad0 drivers/base/dd.c:658
  __driver_probe_device+0x1a2/0x390 drivers/base/dd.c:800
  driver_probe_device+0x50/0x430 drivers/base/dd.c:830
  __driver_attach+0x45f/0x710 drivers/base/dd.c:1216
  bus_for_each_dev+0x239/0x2b0 drivers/base/bus.c:370
  bus_add_driver+0x346/0x670 drivers/base/bus.c:678
 page_owner free stack trace missing

 Memory state around the buggy address:
  ffff888141b0d580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff888141b0d600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 >ffff888141b0d680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                          ^
  ffff888141b0d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff888141b0d780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

Reported-by: syzbot+a5964227adc0f904549c@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=a5964227adc0f904549c
Tested-by: syzbot+a5964227adc0f904549c@...kaller.appspotmail.com
Fixes: e24bbad29a8d ("bpf: Introduce load-acquire and store-release instructions")
Signed-off-by: Kohei Enju <enjuk@...zon.com>
---
 kernel/bpf/verifier.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3303a3605ee8..6481604ab612 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7788,6 +7788,12 @@ static int check_atomic_rmw(struct bpf_verifier_env *env,
 static int check_atomic_load(struct bpf_verifier_env *env,
 			     struct bpf_insn *insn)
 {
+	int err;
+
+	err = check_reg_arg(env, insn->src_reg, SRC_OP);
+	if (err)
+		return err;
+
 	if (!atomic_ptr_type_ok(env, insn->src_reg, insn)) {
 		verbose(env, "BPF_ATOMIC loads from R%d %s is not allowed\n",
 			insn->src_reg,
@@ -7801,6 +7807,12 @@ static int check_atomic_load(struct bpf_verifier_env *env,
 static int check_atomic_store(struct bpf_verifier_env *env,
 			      struct bpf_insn *insn)
 {
+	int err;
+
+	err = check_reg_arg(env, insn->dst_reg, SRC_OP);
+	if (err)
+		return err;
+
 	if (!atomic_ptr_type_ok(env, insn->dst_reg, insn)) {
 		verbose(env, "BPF_ATOMIC stores into R%d %s is not allowed\n",
 			insn->dst_reg,
-- 
2.48.1

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