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 d91c66d3956b..3b11b3b72fe2 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;