| Message ID | 20221209105556.47621-1-ruanjinjie@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: fix a concurrency issue in emulation_proc_handler() | expand |
On Fri, Dec 09, 2022 at 06:55:56PM +0800, ruanjinjie wrote: > 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 The version queued in the arm64 for-next/core branch no longer has the list manipulation, but we do need to fix this for stable, and there is a remaining race on reading insn->current_mode in emulation_proc_handler(). > Fixes: af483947d472 ("arm64: fix oops in concurrently setting insn_emulation sysctls") > Signed-off-by: ruanjinjie <ruanjinjie@huawei.com> > --- > arch/arm64/kernel/armv8_deprecated.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c > index fb0e7c7b2e20..d33e5d9e6990 100644 > --- a/arch/arm64/kernel/armv8_deprecated.c > +++ b/arch/arm64/kernel/armv8_deprecated.c > @@ -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); We don't strictly need to move the container_of(), but it makes no odds either way, and this looks good to me: Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > > if (ret || !write || prev_mode == insn->current_mode) > -- > 2.25.1 >
On 2022/12/9 19:09, Mark Rutland wrote: > On Fri, Dec 09, 2022 at 06:55:56PM +0800, ruanjinjie wrote: >> 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 > > The version queued in the arm64 for-next/core branch no longer has the list > manipulation, but we do need to fix this for stable, and there is a remaining > race on reading insn->current_mode in emulation_proc_handler(). Hi Mark, Should I send this patch to linux-stable? > >> Fixes: af483947d472 ("arm64: fix oops in concurrently setting insn_emulation sysctls") >> Signed-off-by: ruanjinjie <ruanjinjie@huawei.com> >> --- >> arch/arm64/kernel/armv8_deprecated.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c >> index fb0e7c7b2e20..d33e5d9e6990 100644 >> --- a/arch/arm64/kernel/armv8_deprecated.c >> +++ b/arch/arm64/kernel/armv8_deprecated.c >> @@ -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); > > We don't strictly need to move the container_of(), but it makes no odds either > way, and this looks good to me: > > Acked-by: Mark Rutland <mark.rutland@arm.com> > > Mark. > >> >> if (ret || !write || prev_mode == insn->current_mode) >> -- >> 2.25.1 >> >
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c index fb0e7c7b2e20..d33e5d9e6990 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -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)
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: af483947d472 ("arm64: fix oops in concurrently setting insn_emulation sysctls") Signed-off-by: ruanjinjie <ruanjinjie@huawei.com> --- arch/arm64/kernel/armv8_deprecated.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)