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From:   Arnd Bergmann <arnd@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
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Subject: [PATCH v5 1/6] kexec: move locking into do_kexec_load
Date:   Tue, 27 Jul 2021 16:48:54 +0200
Message-Id: <20210727144859.4150043-2-arnd@kernel.org>
In-Reply-To: <20210727144859.4150043-1-arnd@kernel.org>
References: <20210727144859.4150043-1-arnd@kernel.org>
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From: Arnd Bergmann <arnd@arndb.de>

The locking is the same between the native and compat version of
sys_kexec_load(), so it can be done in the common implementation
to reduce duplication.

Co-developed-by: Eric Biederman <ebiederm@xmission.com>
Co-developed-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 kernel/kexec.c | 44 ++++++++++++++++----------------------------
 1 file changed, 16 insertions(+), 28 deletions(-)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index c82c6c06f051..9c7aef8f4bb6 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -110,6 +110,17 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 	unsigned long i;
 	int ret;
 
+	/*
+	 * Because we write directly to the reserved memory region when loading
+	 * crash kernels we need a mutex here to prevent multiple crash kernels
+	 * from attempting to load simultaneously, and to prevent a crash kernel
+	 * from loading over the top of a in use crash kernel.
+	 *
+	 * KISS: always take the mutex.
+	 */
+	if (!mutex_trylock(&kexec_mutex))
+		return -EBUSY;
+
 	if (flags & KEXEC_ON_CRASH) {
 		dest_image = &kexec_crash_image;
 		if (kexec_crash_image)
@@ -121,7 +132,8 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 	if (nr_segments == 0) {
 		/* Uninstall image */
 		kimage_free(xchg(dest_image, NULL));
-		return 0;
+		ret = 0;
+		goto out_unlock;
 	}
 	if (flags & KEXEC_ON_CRASH) {
 		/*
@@ -134,7 +146,7 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 
 	ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
 	if (ret)
-		return ret;
+		goto out_unlock;
 
 	if (flags & KEXEC_PRESERVE_CONTEXT)
 		image->preserve_context = 1;
@@ -171,6 +183,8 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 		arch_kexec_protect_crashkres();
 
 	kimage_free(image);
+out_unlock:
+	mutex_unlock(&kexec_mutex);
 	return ret;
 }
 
@@ -247,21 +261,8 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 		((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 		return -EINVAL;
 
-	/* Because we write directly to the reserved memory
-	 * region when loading crash kernels we need a mutex here to
-	 * prevent multiple crash  kernels from attempting to load
-	 * simultaneously, and to prevent a crash kernel from loading
-	 * over the top of a in use crash kernel.
-	 *
-	 * KISS: always take the mutex.
-	 */
-	if (!mutex_trylock(&kexec_mutex))
-		return -EBUSY;
-
 	result = do_kexec_load(entry, nr_segments, segments, flags);
 
-	mutex_unlock(&kexec_mutex);
-
 	return result;
 }
 
@@ -301,21 +302,8 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 			return -EFAULT;
 	}
 
-	/* Because we write directly to the reserved memory
-	 * region when loading crash kernels we need a mutex here to
-	 * prevent multiple crash  kernels from attempting to load
-	 * simultaneously, and to prevent a crash kernel from loading
-	 * over the top of a in use crash kernel.
-	 *
-	 * KISS: always take the mutex.
-	 */
-	if (!mutex_trylock(&kexec_mutex))
-		return -EBUSY;
-
 	result = do_kexec_load(entry, nr_segments, ksegments, flags);
 
-	mutex_unlock(&kexec_mutex);
-
 	return result;
 }
 #endif
-- 
2.29.2