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Subject[PATCH 2/7] module: take rcu_read_lock_sched for find_symbol
Date
find_symbol() iterates module list with list_for_each_entry_rcu()
should its caller should hold rcu_read_lock_sched().

This patch changes the module_mutex to rcu_read_lock_sched in
resolve_symbol() and adds rcu_read_lock_sched in verify_export_symbols().

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
kernel/module.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 6f6a3fd..b31b23f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1174,7 +1174,7 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
const unsigned long *crc;
int err;

- mutex_lock(&module_mutex);
+ rcu_read_lock_sched();
sym = find_symbol(name, &owner, &crc,
!(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
if (!sym)
@@ -1196,7 +1196,7 @@ getname:
/* We must make copy under the lock if we failed to get ref. */
strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
unlock:
- mutex_unlock(&module_mutex);
+ rcu_read_unlock_sched();
return sym;
}

@@ -1844,6 +1844,7 @@ static int verify_export_symbols(struct module *mod)
#endif
};

+ rcu_read_lock_sched();
for (i = 0; i < ARRAY_SIZE(arr); i++) {
for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
if (find_symbol(s->name, &owner, NULL, true, false)) {
@@ -1851,10 +1852,12 @@ static int verify_export_symbols(struct module *mod)
"%s: exports duplicate symbol %s"
" (owned by %s)\n",
mod->name, s->name, module_name(owner));
+ rcu_read_unlock_sched();
return -ENOEXEC;
}
}
}
+ rcu_read_unlock_sched();
return 0;
}

--
1.7.7.6


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