autofs: harden 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) <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Acked-by: Ian Kent <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Oct 16, 2020 · 589f6b5 · 589f6b5
1 parent 50b7d85
commit 589f6b5
Showing 1 changed file with 6 additions and 2 deletions.
diff --git 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 */