From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 11 Sep 2013 21:24:41 +0000 (-0700)
Subject: exec: move allow_write_access/fput to exec_binprm()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=52f14282bb0c3d3e5ba2a9eaacb12ff37a033e7e;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

exec: move allow_write_access/fput to exec_binprm()

When search_binary_handler() succeeds it does allow_write_access() and
fput(), then it clears bprm->file to ensure the caller will not do the
same.

We can simply move this code to exec_binprm() which is called only once.
In fact we could move this to free_bprm() and remove the same code in
do_execve_common's error path.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Zach Levis <zml@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/exec.c b/fs/exec.c
index d51f7172832b..a4cfd1d725e0 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1400,10 +1400,6 @@ int search_binary_handler(struct linux_binprm *bprm)
 			bprm->recursion_depth--;
 			if (retval >= 0) {
 				put_binfmt(fmt);
-				allow_write_access(bprm->file);
-				if (bprm->file)
-					fput(bprm->file);
-				bprm->file = NULL;
 				return retval;
 			}
 			read_lock(&binfmt_lock);
@@ -1455,6 +1451,12 @@ static int exec_binprm(struct linux_binprm *bprm)
 		ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
 		current->did_exec = 1;
 		proc_exec_connector(current);
+
+		if (bprm->file) {
+			allow_write_access(bprm->file);
+			fput(bprm->file);
+			bprm->file = NULL; /* to catch use-after-free */
+		}
 	}
 
 	return ret;