diff options
| author | Jingwei Wang <wangjingwei@iscas.ac.cn> | 2025-08-11 22:20:06 +0800 |
|---|---|---|
| committer | Paul Walmsley <pjw@kernel.org> | 2025-10-17 22:23:11 -0600 |
| commit | 5d15d2ad36b0f7afab83ca9fc8a2a6e60cbe54c4 (patch) | |
| tree | 5b38e5c8eb0474134a105ec828246f20b0674c89 /arch/riscv/kernel/vdso | |
| parent | 492c513ec6de1ce51b5f033bd6c708e4b8e46ae4 (diff) | |
riscv: hwprobe: Fix stale vDSO data for late-initialized keys at boot
The hwprobe vDSO data for some keys, like MISALIGNED_VECTOR_PERF,
is determined by an asynchronous kthread. This can create a race
condition where the kthread finishes after the vDSO data has
already been populated, causing userspace to read stale values.
To fix this race, a new 'ready' flag is added to the vDSO data,
initialized to 'false' during arch_initcall_sync. This flag is
checked by both the vDSO's user-space code and the riscv_hwprobe
syscall. The syscall serves as a one-time gate, using a completion
to wait for any pending probes before populating the data and
setting the flag to 'true', thus ensuring userspace reads fresh
values on its first request.
Reported-by: Tsukasa OI <research_trasio@irq.a4lg.com>
Closes: https://lore.kernel.org/linux-riscv/760d637b-b13b-4518-b6bf-883d55d44e7f@irq.a4lg.com/
Fixes: e7c9d66e313b ("RISC-V: Report vector unaligned access speed hwprobe")
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: stable@vger.kernel.org
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Co-developed-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Jingwei Wang <wangjingwei@iscas.ac.cn>
Link: https://lore.kernel.org/r/20250811142035.105820-1-wangjingwei@iscas.ac.cn
[pjw@kernel.org: fix checkpatch issues]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Diffstat (limited to 'arch/riscv/kernel/vdso')
| -rw-r--r-- | arch/riscv/kernel/vdso/hwprobe.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/riscv/kernel/vdso/hwprobe.c b/arch/riscv/kernel/vdso/hwprobe.c index 2ddeba6c68dd..8f45500d0a6e 100644 --- a/arch/riscv/kernel/vdso/hwprobe.c +++ b/arch/riscv/kernel/vdso/hwprobe.c @@ -27,7 +27,7 @@ static int riscv_vdso_get_values(struct riscv_hwprobe *pairs, size_t pair_count, * homogeneous, then this function can handle requests for arbitrary * masks. */ - if ((flags != 0) || (!all_cpus && !avd->homogeneous_cpus)) + if (flags != 0 || (!all_cpus && !avd->homogeneous_cpus) || unlikely(!avd->ready)) return riscv_hwprobe(pairs, pair_count, cpusetsize, cpus, flags); /* This is something we can handle, fill out the pairs. */ |