[PATCH 5.10 1/3] kexec: move locking into do_kexec_load - Linux-stable-mirror

1 Mar 2023

From: Arnd Bergmann arnd@arndb.de
commit 4b692e861619353ce069e547a67c8d0e32d9ef3d upstream.
Patch series "compat: remove compat_alloc_user_space", v5.
Going through compat_alloc_user_space() to convert indirect system call
arguments tends to add complexity compared to handling the native and
compat logic in the same code.
This patch (of 6):
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.
Link: https://lkml.kernel.org/r/20210727144859.4150043-1-arnd@kernel.org
Link: https://lkml.kernel.org/r/20210727144859.4150043-2-arnd@kernel.org
Signed-off-by: Arnd Bergmann arnd@arndb.de
Co-developed-by: Eric Biederman ebiederm@xmission.com
Co-developed-by: Christoph Hellwig hch@infradead.org
Acked-by: "Eric W. Biederman" ebiederm@xmission.com
Cc: Catalin Marinas catalin.marinas@arm.com
Cc: Will Deacon will@kernel.org
Cc: Thomas Bogendoerfer tsbogend@alpha.franken.de
Cc: "James E.J. Bottomley" James.Bottomley@HansenPartnership.com
Cc: Helge Deller deller@gmx.de
Cc: Michael Ellerman mpe@ellerman.id.au
Cc: Benjamin Herrenschmidt benh@kernel.crashing.org
Cc: Paul Mackerras paulus@samba.org
Cc: Heiko Carstens hca@linux.ibm.com
Cc: Vasily Gorbik gor@linux.ibm.com
Cc: Christian Borntraeger borntraeger@de.ibm.com
Cc: "David S. Miller" davem@davemloft.net
Cc: Thomas Gleixner tglx@linutronix.de
Cc: Ingo Molnar mingo@redhat.com
Cc: Borislav Petkov bp@alien8.de
Cc: "H. Peter Anvin" hpa@zytor.com
Cc: Al Viro viro@zeniv.linux.org.uk
Cc: Feng Tang feng.tang@intel.com
Cc: Christoph Hellwig hch@lst.de
Signed-off-by: Andrew Morton akpm@linux-foundation.org
Signed-off-by: Linus Torvalds torvalds@linux-foundation.org
Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Wen Yang wenyang.linux@foxmail.com
---
 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
-- 
2.37.2


    