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Subject[PATCH] Harden autofs ioctl table
The table of ioctl functions should be marked const in order to put them
in read-only memory, and we should use array_index_nospec() to avoid
speculation disclosing the contents of kernel memory to userspace.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/fs/autofs/dev-ioctl.c b/fs/autofs/dev-ioctl.c
index 75105f45c51a..322b7dfb4ea0 100644
--- a/fs/autofs/dev-ioctl.c
+++ b/fs/autofs/dev-ioctl.c
@@ -8,6 +8,7 @@
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/magic.h>
+#include <linux/nospec.h>

#include "autofs_i.h"

@@ -563,7 +564,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,

static ioctl_fn lookup_dev_ioctl(unsigned int cmd)
{
- static ioctl_fn _ioctls[] = {
+ static const ioctl_fn _ioctls[] = {
autofs_dev_ioctl_version,
autofs_dev_ioctl_protover,
autofs_dev_ioctl_protosubver,
@@ -581,7 +582,10 @@ static ioctl_fn lookup_dev_ioctl(unsigned int cmd)
};
unsigned int idx = cmd_idx(cmd);

- return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx];
+ if (idx >= ARRAY_SIZE(_ioctls))
+ return NULL;
+ idx = array_index_nospec(idx, ARRAY_SIZE(_ioctls));
+ return _ioctls[idx];
}

/* ioctl dispatcher */
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