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Subject[PATCH kernel] srcu: Fix static initialization
Date
init_srcu_struct_nodes() is called with is_static==true only internally
and when this happens, the srcu->sda is not initialized in
init_srcu_struct_fields() and we crash on dereferencing @sdp.

This fixes the crash by moving "if (is_static)" out of the loop which
only does useful work for is_static=false case anyway.

Found by syzkaller.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
kernel/rcu/srcutree.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index c100acf332ed..49b54a50bde8 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -135,6 +135,9 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
levelspread[level - 1];
}

+ if (is_static)
+ return;
+
/*
* Initialize the per-CPU srcu_data array, which feeds into the
* leaves of the srcu_node tree.
@@ -161,8 +164,6 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
timer_setup(&sdp->delay_work, srcu_delay_timer, 0);
sdp->ssp = ssp;
sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
- if (is_static)
- continue;

/* Dynamically allocated, better be no srcu_read_locks()! */
for (i = 0; i < ARRAY_SIZE(sdp->srcu_lock_count); i++) {
--
2.17.1
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