Messages in this thread Patch in this message | | | From | haibinzhang(张海斌) <> | Subject | [PATCH V2] arm64: fix oops in concurrently setting insn_emulation sysctls | Date | Sat, 2 Jul 2022 05:43:19 +0000 |
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How to reproduce: launch two shell executions: #!/bin/bash while [ 1 ]; do echo 1 > /proc/sys/abi/swp done
Oops info: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 Internal error: Oops: 96000006 [#1] SMP Call trace: update_insn_emulation_mode+0xc0/0x148 emulation_proc_handler+0x64/0xb8 proc_sys_call_handler+0x9c/0xf8 proc_sys_write+0x18/0x20 __vfs_write+0x20/0x48 vfs_write+0xe4/0x1d0 ksys_write+0x70/0xf8 __arm64_sys_write+0x20/0x28 el0_svc_common.constprop.0+0x7c/0x1c0 el0_svc_handler+0x2c/0xa0 el0_svc+0x8/0x200
emulation_proc_handler changes table->data for proc_dointvec_minmax and so it isn't allowed to reenter before restoring table->data, which isn't right now. To fix this issue, keep the table->data as &insn->current_mode and use container_of() to retrieve the insn pointer. Another mutex is used to protect against the current_mode update but not for retrieving insn_emulation as table->data is no longer changing.
Signed-off-by: hewenliang <hewenliang4@huawei.com> Signed-off-by: Haibin Zhang <haibinzhang@tencent.com> --- arch/arm64/kernel/armv8_deprecated.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c index 6875a16b09d2..fb0e7c7b2e20 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -59,6 +59,7 @@ struct insn_emulation { static LIST_HEAD(insn_emulation); static int nr_insn_emulated __initdata; static DEFINE_RAW_SPINLOCK(insn_emulation_lock); +static DEFINE_MUTEX(insn_emulation_mutex); static void register_emulation_hooks(struct insn_emulation_ops *ops) { @@ -207,10 +208,10 @@ static int emulation_proc_handler(struct ctl_table *table, int write, loff_t *ppos) { int ret = 0; - struct insn_emulation *insn = (struct insn_emulation *) table->data; + struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode); enum insn_emulation_mode prev_mode = insn->current_mode; - table->data = &insn->current_mode; + mutex_lock(&insn_emulation_mutex); ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (ret || !write || prev_mode == insn->current_mode) @@ -223,7 +224,7 @@ static int emulation_proc_handler(struct ctl_table *table, int write, update_insn_emulation_mode(insn, INSN_UNDEF); } ret: - table->data = insn; + mutex_unlock(&insn_emulation_mutex); return ret; } @@ -247,7 +248,7 @@ static void __init register_insn_emulation_sysctl(void) sysctl->maxlen = sizeof(int); sysctl->procname = insn->ops->name; - sysctl->data = insn; + sysctl->data = &insn->current_mode; sysctl->extra1 = &insn->min; sysctl->extra2 = &insn->max; sysctl->proc_handler = emulation_proc_handler; -- 2.34.1
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