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Subject[PATCH 17/17] module: Prevent module removal racing with text_poke()
Date
From: Nadav Amit <namit@vmware.com>

It seems dangerous to allow code modifications to take place
concurrently with module unloading. So take the text_mutex while the
memory of the module is freed.

Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
kernel/module.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 1af5c8e19086..90cfc4988d98 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -64,6 +64,7 @@
#include <linux/bsearch.h>
#include <linux/dynamic_debug.h>
#include <linux/audit.h>
+#include <linux/memory.h>
#include <uapi/linux/module.h>
#include "module-internal.h"

@@ -2157,6 +2158,9 @@ static void free_module(struct module *mod)
synchronize_rcu();
mutex_unlock(&module_mutex);

+ /* Protect against patching of the module while it is being removed */
+ mutex_lock(&text_mutex);
+
/* This may be empty, but that's OK */
module_arch_freeing_init(mod);
module_memfree(mod->init_layout.base);
@@ -2168,6 +2172,7 @@ static void free_module(struct module *mod)

/* Finally, free the core (containing the module structure) */
module_memfree(mod->core_layout.base);
+ mutex_unlock(&text_mutex);
}

void *__symbol_get(const char *symbol)
--
2.17.1
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