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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>
af483947d4