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arm64: fix oops in concurrently setting insn_emulation sysctls
[ Upstream commit af483947d4
]
emulation_proc_handler() changes table->data for proc_dointvec_minmax
and can generate the following Oops if called concurrently with itself:
| 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
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.
Co-developed-by: hewenliang <hewenliang4@huawei.com>
Signed-off-by: hewenliang <hewenliang4@huawei.com>
Signed-off-by: Haibin Zhang <haibinzhang@tencent.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220128090324.2727688-1-hewenliang4@huawei.com
Link: https://lore.kernel.org/r/9A004C03-250B-46C5-BF39-782D7551B00E@tencent.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
fa09c39265
commit
04549063d5
1 changed files with 5 additions and 4 deletions
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@ -59,6 +59,7 @@ struct insn_emulation {
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static LIST_HEAD(insn_emulation);
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static int nr_insn_emulated __initdata;
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static DEFINE_RAW_SPINLOCK(insn_emulation_lock);
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static DEFINE_MUTEX(insn_emulation_mutex);
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static void register_emulation_hooks(struct insn_emulation_ops *ops)
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{
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@ -207,10 +208,10 @@ static int emulation_proc_handler(struct ctl_table *table, int write,
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loff_t *ppos)
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{
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int ret = 0;
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struct insn_emulation *insn = (struct insn_emulation *) table->data;
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struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode);
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enum insn_emulation_mode prev_mode = insn->current_mode;
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table->data = &insn->current_mode;
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mutex_lock(&insn_emulation_mutex);
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ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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if (ret || !write || prev_mode == insn->current_mode)
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@ -223,7 +224,7 @@ static int emulation_proc_handler(struct ctl_table *table, int write,
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update_insn_emulation_mode(insn, INSN_UNDEF);
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}
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ret:
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table->data = insn;
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mutex_unlock(&insn_emulation_mutex);
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return ret;
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}
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@ -247,7 +248,7 @@ static void __init register_insn_emulation_sysctl(void)
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sysctl->maxlen = sizeof(int);
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sysctl->procname = insn->ops->name;
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sysctl->data = insn;
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sysctl->data = &insn->current_mode;
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sysctl->extra1 = &insn->min;
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sysctl->extra2 = &insn->max;
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sysctl->proc_handler = emulation_proc_handler;
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