take security_mmap_file() outside of ->mmap_sem

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 30 insertions, 3 deletions

diff --git a/security/security.c b/security/security.c
index d91c66d3956..3b11b3b72fe 100644
--- a/security/security.c
+++ b/security/security.c
@@ -20,6 +20,9 @@
 #include <linux/ima.h>
 #include <linux/evm.h>
 #include <linux/fsnotify.h>
+#include <linux/mman.h>
+#include <linux/mount.h>
+#include <linux/personality.h>
 #include <net/flow.h>
 
 #define MAX_LSM_EVM_XATTR	2
@@ -657,11 +660,35 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	return security_ops->file_ioctl(file, cmd, arg);
 }
 
-int security_mmap_file(struct file *file, unsigned long reqprot,
-			unsigned long prot, unsigned long flags)
+int security_mmap_file(struct file *file, unsigned long prot,
+			unsigned long flags)
 {
+	unsigned long reqprot = prot;
 	int ret;
-
+	/*
+	 * Does the application expect PROT_READ to imply PROT_EXEC?
+	 *
+	 * (the exception is when the underlying filesystem is noexec
+	 *  mounted, in which case we dont add PROT_EXEC.)
+	 */
+	if (!(reqprot & PROT_READ))
+		goto out;
+	if (!(current->personality & READ_IMPLIES_EXEC))
+		goto out;
+	if (!file) {
+		prot |= PROT_EXEC;
+	} else if (!(file->f_path.mnt->mnt_flags & MNT_NOEXEC)) {
+#ifndef CONFIG_MMU
+		unsigned long caps = 0;
+		struct address_space *mapping = file->f_mapping;
+		if (mapping && mapping->backing_dev_info)
+			caps = mapping->backing_dev_info->capabilities;
+		if (!(caps & BDI_CAP_EXEC_MAP))
+			goto out;
+#endif
+		prot |= PROT_EXEC;
+	}
+out:
 	ret = security_ops->mmap_file(file, reqprot, prot, flags);
 	if (ret)
 		return ret;