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Subject[PATCH v2 1/4] kexec: simplify compat_sys_kexec_load
Date
From: Arnd Bergmann <arnd@arndb.de>

The compat version of sys_kexec_load() uses compat_alloc_user_space to
convert the user-provided arguments into the native format.

Move the conversion into the regular implementation with
an in_compat_syscall() check to simplify it and avoid the
compat_alloc_user_space() call.

compat_sys_kexec_load() now behaves the same as sys_kexec_load().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
include/linux/kexec.h | 2 -
kernel/kexec.c | 95 +++++++++++++++++++------------------------
2 files changed, 42 insertions(+), 55 deletions(-)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 9e93bef52968..7b6717cd5c4a 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -88,14 +88,12 @@ struct kexec_segment {
size_t memsz;
};

-#ifdef CONFIG_COMPAT
struct compat_kexec_segment {
compat_uptr_t buf;
compat_size_t bufsz;
compat_ulong_t mem; /* User space sees this as a (void *) ... */
compat_size_t memsz;
};
-#endif

#ifdef CONFIG_KEXEC_FILE
struct purgatory_info {
diff --git a/kernel/kexec.c b/kernel/kexec.c
index c82c6c06f051..ec04791eea3e 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -19,21 +19,46 @@

#include "kexec_internal.h"

+static int copy_user_compat_segment_list(struct kimage *image,
+ unsigned long nr_segments,
+ void __user *segments)
+{
+ struct compat_kexec_segment __user *cs = segments;
+ struct compat_kexec_segment segment;
+ int i;
+
+ for (i=0; i < nr_segments; i++) {
+ if (copy_from_user(&segment, &cs[i], sizeof(segment)))
+ return -EFAULT;
+
+ image->segment[i] = (struct kexec_segment) {
+ .buf = compat_ptr(segment.buf),
+ .bufsz = segment.bufsz,
+ .mem = segment.mem,
+ .memsz = segment.memsz,
+ };
+ }
+
+ return 0;
+}
+
+
static int copy_user_segment_list(struct kimage *image,
unsigned long nr_segments,
struct kexec_segment __user *segments)
{
- int ret;
size_t segment_bytes;

/* Read in the segments */
image->nr_segments = nr_segments;
segment_bytes = nr_segments * sizeof(*segments);
- ret = copy_from_user(image->segment, segments, segment_bytes);
- if (ret)
- ret = -EFAULT;
+ if (in_compat_syscall())
+ return copy_user_compat_segment_list(image, nr_segments, segments);

- return ret;
+ if (copy_from_user(image->segment, segments, segment_bytes))
+ return -EFAULT;
+
+ return 0;
}

static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
@@ -233,8 +258,9 @@ static inline int kexec_load_check(unsigned long nr_segments,
return 0;
}

-SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
- struct kexec_segment __user *, segments, unsigned long, flags)
+static int kernel_kexec_load(unsigned long entry, unsigned long nr_segments,
+ struct kexec_segment __user * segments,
+ unsigned long flags)
{
int result;

@@ -265,57 +291,20 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
return result;
}

+SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
+ struct kexec_segment __user *, segments, unsigned long, flags)
+{
+ return kernel_kexec_load(entry, nr_segments, segments, flags);
+}
+
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
compat_ulong_t, nr_segments,
struct compat_kexec_segment __user *, segments,
compat_ulong_t, flags)
{
- struct compat_kexec_segment in;
- struct kexec_segment out, __user *ksegments;
- unsigned long i, result;
-
- result = kexec_load_check(nr_segments, flags);
- if (result)
- return result;
-
- /* Don't allow clients that don't understand the native
- * architecture to do anything.
- */
- if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
- return -EINVAL;
-
- ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
- for (i = 0; i < nr_segments; i++) {
- result = copy_from_user(&in, &segments[i], sizeof(in));
- if (result)
- return -EFAULT;
-
- out.buf = compat_ptr(in.buf);
- out.bufsz = in.bufsz;
- out.mem = in.mem;
- out.memsz = in.memsz;
-
- result = copy_to_user(&ksegments[i], &out, sizeof(out));
- if (result)
- 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;
+ return kernel_kexec_load(entry, nr_segments,
+ (struct kexec_segment __user *)segments,
+ flags);
}
#endif
--
2.27.0
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