exec: binfmt_misc: kill the onstack iname[BINPRM_BUF_SIZE] array

After the previous change "fmt" can't go away, we can kill
iname/iname_addr and use fmt->interpreter.

Link: http://lkml.kernel.org/r/20170922143653.GA17232@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ben Woodard <woodard@redhat.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jim Foraker <foraker1@llnl.gov>
Cc: <tdhooge@llnl.gov>
Cc: Travis Gummels <tgummels@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index f5f8c25..2a46762 100644 (file)
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -54,7 +54,7 @@ typedef struct {
        int size;                       /* size of magic/mask */
        char *magic;                    /* magic or filename extension */
        char *mask;                     /* mask, NULL for exact match */
-       char *interpreter;              /* filename of interpreter */
+       const char *interpreter;        /* filename of interpreter */
        char *name;
        struct dentry *dentry;
        struct file *interp_file;
@@ -131,8 +131,6 @@ static int load_misc_binary(struct linux_binprm *bprm)
 {
        Node *fmt;
        struct file *interp_file = NULL;
-       char iname[BINPRM_BUF_SIZE];
-       const char *iname_addr = iname;
        int retval;
        int fd_binary = -1;
 
@@ -143,10 +141,8 @@ static int load_misc_binary(struct linux_binprm *bprm)
        /* to keep locking time low, we copy the interpreter string */
        read_lock(&entries_lock);
        fmt = check_file(bprm);
-       if (fmt) {
+       if (fmt)
                dget(fmt->dentry);
-               strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
-       }
        read_unlock(&entries_lock);
        if (!fmt)
                return retval;
@@ -198,13 +194,13 @@ static int load_misc_binary(struct linux_binprm *bprm)
        bprm->argc++;
 
        /* add the interp as argv[0] */
-       retval = copy_strings_kernel(1, &iname_addr, bprm);
+       retval = copy_strings_kernel(1, &fmt->interpreter, bprm);
        if (retval < 0)
                goto error;
        bprm->argc++;
 
        /* Update interp in case binfmt_script needs it. */
-       retval = bprm_change_interp(iname, bprm);
+       retval = bprm_change_interp(fmt->interpreter, bprm);
        if (retval < 0)
                goto error;
 
@@ -213,7 +209,7 @@ static int load_misc_binary(struct linux_binprm *bprm)
                if (!IS_ERR(interp_file))
                        deny_write_access(interp_file);
        } else {
-               interp_file = open_exec(iname);
+               interp_file = open_exec(fmt->interpreter);
        }
        retval = PTR_ERR(interp_file);
        if (IS_ERR(interp_file))