From: Linus Torvalds torvalds@linuxfoundation.org

stable inclusion from stable-v4.19.307 commit 3cd139875e9a7688b3fc715264032620812a5fa3 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I93SNV CVE: CVE-2024-26602

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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commit 944d5fe50f3f03daacfea16300e656a1691c4a23 upstream.

On some systems, sys_membarrier can be very expensive, causing overall slowdowns for everything. So put a lock on the path in order to serialize the accesses to prevent the ability for this to be called at too high of a frequency and saturate the machine.

Reviewed-and-tested-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Acked-by: Borislav Petkov bp@alien8.de Fixes: 22e4ebb97582 ("membarrier: Provide expedited private command") Fixes: c5f58bd58f43 ("membarrier: Provide GLOBAL_EXPEDITED command") Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ converted to explicit mutex_*() calls - cleanup.h is not in this stable branch - gregkh ] Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zhao Wenhui zhaowenhui8@huawei.com --- kernel/sched/membarrier.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index 1757074be994..4978b8fe59e5 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -34,6 +34,8 @@ | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED \ | MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK)

+static DEFINE_MUTEX(membarrier_ipi_mutex); + static void ipi_mb(void *info) { smp_mb(); /* IPIs should be serializing but paranoid. */ @@ -89,6 +91,7 @@ static int membarrier_global_expedited(void) if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) return -ENOMEM;

+ mutex_lock(&membarrier_ipi_mutex); cpus_read_lock(); rcu_read_lock(); for_each_online_cpu(cpu) { @@ -135,6 +138,7 @@ static int membarrier_global_expedited(void) * rq->curr modification in scheduler. */ smp_mb(); /* exit from system call is not a mb */ + mutex_unlock(&membarrier_ipi_mutex); return 0; }

@@ -168,6 +172,7 @@ static int membarrier_private_expedited(int flags) if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) return -ENOMEM;

+ mutex_lock(&membarrier_ipi_mutex); cpus_read_lock(); rcu_read_lock(); for_each_online_cpu(cpu) { @@ -202,6 +207,7 @@ static int membarrier_private_expedited(int flags) * rq->curr modification in scheduler. */ smp_mb(); /* exit from system call is not a mb */ + mutex_unlock(&membarrier_ipi_mutex);

return 0; }