"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@vger.kernel.org Signed-off-by: Chen Zhongjin chenzhongjin@huawei.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))