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Date: Wed, 16 Jan 2019 16:32:59 -0800
From: Rick Edgecombe <rick.p.edgecombe@...el.com>
To: Andy Lutomirski <luto@...nel.org>,
Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org,
x86@...nel.org,
hpa@...or.com,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
Nadav Amit <nadav.amit@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
linux_dti@...oud.com,
linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
akpm@...ux-foundation.org,
kernel-hardening@...ts.openwall.com,
linux-mm@...ck.org,
will.deacon@....com,
ard.biesheuvel@...aro.org,
kristen@...ux.intel.com,
deneen.t.dock@...el.com,
Nadav Amit <namit@...are.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>
Subject: [PATCH 17/17] module: Prevent module removal racing with text_poke()
From: Nadav Amit <namit@...are.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@...are.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.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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