[PATCH] sys_hpux: fix strlen_user() race

Userspace can alter the string after the kernel has run strlen_user().

Also: the strlen_user() return value includes the \0, so fix that.

Also: handle EFAULT from strlen_user().

It's unlikely anyone is using this code.  Very, very unlikely.  If I
remember correctly, CONFIG_HPUX turns this code on, but one would actually
need CONFIG_BINFMT_SOM to load a binary that could cause a problem, and
BINFMT_SOM has had an #error in it for quite some time.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/parisc/hpux/sys_hpux.c b/arch/parisc/hpux/sys_hpux.c
index 29b4d61898f2..05273ccced0e 100644
--- a/arch/parisc/hpux/sys_hpux.c
+++ b/arch/parisc/hpux/sys_hpux.c
@@ -468,19 +468,23 @@ int hpux_sysfs(int opcode, unsigned long arg1, unsigned long arg2)
         if ( opcode == 1 ) { /* GETFSIND */     
                 len = strlen_user((char *)arg1);
                 printk(KERN_DEBUG "len of arg1 = %d\n", len);
-
-                fsname = (char *) kmalloc(len+1, GFP_KERNEL);
+                if (len == 0)
+                        return 0;
+                fsname = (char *) kmalloc(len, GFP_KERNEL);
                 if ( !fsname ) {
                         printk(KERN_DEBUG "failed to kmalloc fsname\n");
                         return 0;
                 }
 
-                if ( copy_from_user(fsname, (char *)arg1, len+1) ) {
+                if ( copy_from_user(fsname, (char *)arg1, len) ) {
                         printk(KERN_DEBUG "failed to copy_from_user fsname\n");
                         kfree(fsname);
                         return 0;
                 }
 
+                /* String could be altered by userspace after strlen_user() */
+                fsname[len] = '\0';
+
                 printk(KERN_DEBUG "that is '%s' as (char *)\n", fsname);
                 if ( !strcmp(fsname, "hfs") ) {
                         fstype = 0;