提交 36e1d5c0 编写于 作者: R ruanjinjie 提交者: Zheng Zengkai

arm64: fix a concurrency issue in emulation_proc_handler()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I65RG3?from=project-issue
CVE: NA

-------------------------------

In emulation_proc_handler(), read and write operations are performed on
insn->current_mode. In the concurrency scenario, mutex only protects
writing insn->current_mode, and not protects the read. Suppose there are
two concurrent tasks, task1 updates insn->current_mode to INSN_EMULATE
in the critical section, the prev_mode of task2 is still the old data
INSN_UNDEF of insn->current_mode. As a result, two tasks call
update_insn_emulation_mode twice with prev_mode = INSN_UNDEF and
current_mode = INSN_EMULATE, then call register_emulation_hooks twice,
resulting in a list_add double problem.

Call trace:
 __list_add_valid+0xd8/0xe4
 register_undef_hook+0x94/0x13c
 update_insn_emulation_mode+0xd0/0x12c
 emulation_proc_handler+0xd8/0xf4
 proc_sys_call_handler+0x140/0x250
 proc_sys_write+0x1c/0x2c
 new_sync_write+0xec/0x18c
 vfs_write+0x214/0x2ac
 ksys_write+0x70/0xfc
 __arm64_sys_write+0x24/0x30
 el0_svc_common.constprop.0+0x7c/0x1bc
 do_el0_svc+0x2c/0x94
 el0_svc+0x20/0x30
 el0_sync_handler+0xb0/0xb4
 el0_sync+0x160/0x180

Fixes: fcddf02a ("arm64: fix oops in concurrently setting insn_emulation sysctls")
Signed-off-by: Nruanjinjie <ruanjinjie@huawei.com>
Reviewed-by: NLiao Chang <liaochang1@huawei.com>
Reviewed-by: NZhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
上级 ce4fbc28
......@@ -208,10 +208,12 @@ static int emulation_proc_handler(struct ctl_table *table, int write,
loff_t *ppos)
{
int ret = 0;
struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode);
enum insn_emulation_mode prev_mode = insn->current_mode;
struct insn_emulation *insn;
enum insn_emulation_mode prev_mode;
mutex_lock(&insn_emulation_mutex);
insn = container_of(table->data, struct insn_emulation, current_mode);
prev_mode = insn->current_mode;
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (ret || !write || prev_mode == insn->current_mode)
......
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