linux-kernel - [PATCH] profiling: fix shift too large makes kernel panic

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Message-ID: <20220531012854.229439-1-chenzhongjin@huawei.com>
Date:   Tue, 31 May 2022 09:28:54 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
CC:     <ebiederm@...ssion.com>, <akpm@...ux-foundation.org>,
        <paskripkin@...il.com>, <chenzhongjin@...wei.com>
Subject: [PATCH] profiling: fix shift too large makes kernel panic

"2d186afd04d6: profiling: fix shift-out-of-bounds bugs" limits shift
value by [0, BITS_PER_LONG -1], which means [0, 63].

However, syzbot found that the max shift value should be the bit number
of (_etext - _stext). If shift be out of this, the "buffer_bytes" will
be zero and cause kzalloc(0). Then kernel goes panic for derefrence
returned pointer 16.

It can be easily reproduced by pass a large number like 60 to enable
profiling and then run readprofile.

LOGS:
 BUG: kernel NULL pointer dereference, address: 0000000000000010
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 PGD 6148067 P4D 6148067 PUD 6142067 PMD 0
 PREEMPT SMP
 CPU: 4 PID: 184 Comm: readprofile Not tainted 5.18.0+ #162
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
 RIP: 0010:read_profile+0x104/0x220
 RSP: 0018:ffffc900006fbe80 EFLAGS: 00000202
 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
 RDX: ffff888006150000 RSI: 0000000000000001 RDI: ffffffff82aba4a0
 RBP: 000000000188bb60 R08: 0000000000000010 R09: ffff888006151000
 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82aba4a0
 R13: 0000000000000000 R14: ffffc900006fbf08 R15: 0000000000020c30
 FS:  000000000188a8c0(0000) GS:ffff88803ed00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000010 CR3: 0000000006144000 CR4: 00000000000006e0
 Call Trace:
  <TASK>
  proc_reg_read+0x56/0x70
  vfs_read+0x9a/0x1b0
  ksys_read+0xa1/0xe0
  ? fpregs_assert_state_consistent+0x1e/0x40
  do_syscall_64+0x3a/0x80
  entry_SYSCALL_64_after_hwframe+0x46/0xb0
 RIP: 0033:0x4d4b4e
 RSP: 002b:00007ffebb668d58 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
 RAX: ffffffffffffffda RBX: 000000000188a8a0 RCX: 00000000004d4b4e
 RDX: 0000000000000400 RSI: 000000000188bb60 RDI: 0000000000000003
 RBP: 0000000000000003 R08: 000000000000006e R09: 0000000000000000
 R10: 0000000000000041 R11: 0000000000000246 R12: 000000000188bb60
 R13: 0000000000000400 R14: 0000000000000000 R15: 000000000188bb60
  </TASK>
 Modules linked in:
 CR2: 0000000000000010
Killed
 ---[ end trace 0000000000000000 ]---

Check prof_len in profile_init() to prevent it be zero.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@...r.kernel.org
Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
---
 kernel/profile.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/profile.c b/kernel/profile.c
index 37640a0bd8a3..ae82ddfc6a68 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -109,6 +109,13 @@ int __ref profile_init(void)
 
 	/* only text is profiled */
 	prof_len = (_etext - _stext) >> prof_shift;
+
+	if (!prof_len) {
+		pr_warn("profiling shift: %u too large\n", prof_shift);
+		prof_on = 0;
+		return -EINVAL;
+	}
+
 	buffer_bytes = prof_len*sizeof(atomic_t);
 
 	if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
-- 
2.17.1