From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 1 Dec 2010 16:43:50 -0500
Subject: [fs] exec: copy fixes into compat_do_execve paths
Message-id: <20101201164350.GF1758@redhat.com>
Patchwork-id: 29772
O-Subject: [RHEL5.6 PATCH 3/3] bz625694: exec: copy-and-paste the fixes into
	compat_do_execve() paths
Bugzilla: 625694
CVE: CVE-2010-4243

https://bugzilla.redhat.com/show_bug.cgi?id=625694

Upsteram commit 114279be2120a916e8a04feeb2ac976a10016f2f
Author: Oleg Nesterov <oleg@redhat.com>
Date:   Tue Nov 30 20:56:02 2010 +0100

    exec: copy-and-paste the fixes into compat_do_execve() paths

    Note: this patch targets 2.6.37 and tries to be as simple as possible.
    That is why it adds more copy-and-paste horror into fs/compat.c and
    uglifies fs/exec.c, this will be cleanuped later.

    compat_copy_strings() plays with bprm->vma/mm directly and thus has
    two problems: it lacks the RLIMIT_STACK check and argv/envp memory
    is not visible to oom killer.

    Export acct_arg_size() and get_arg_page(), change compat_copy_strings()
    to use get_arg_page(), change compat_do_execve() to do acct_arg_size(0)
    as do_execve() does.

    Add the fatal_signal_pending/cond_resched checks into compat_count() and
    compat_copy_strings(), this matches the code in fs/exec.c and certainly
    makes sense.

    Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: stable@kernel.org
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Note: as for cleanups mentioned in the changelog, I sent them upstream
but I don't think this is RHEL material.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

diff --git a/fs/compat.c b/fs/compat.c
index c77b194..0405487 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1427,6 +1427,10 @@ static int compat_count(compat_uptr_t __user *argv, int max)
 			argv++;
 			if(++i > max)
 				return -E2BIG;
+
+			if (fatal_signal_pending(current))
+				return -ERESTARTNOHAND;
+			cond_resched();
 		}
 	}
 	return i;
@@ -1468,6 +1472,12 @@ static int compat_copy_strings(int argc, compat_uptr_t __user *argv,
 		while (len > 0) {
 			int offset, bytes_to_copy;
 
+			if (fatal_signal_pending(current)) {
+				ret = -ERESTARTNOHAND;
+				goto out;
+			}
+			cond_resched();
+
 			offset = pos % PAGE_SIZE;
 			if (offset == 0)
 				offset = PAGE_SIZE;
@@ -1484,18 +1494,8 @@ static int compat_copy_strings(int argc, compat_uptr_t __user *argv,
 			if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 				struct page *page;
 
-#ifdef CONFIG_STACK_GROWSUP
-				ret = expand_stack_downwards(bprm->vma, pos);
-				if (ret < 0) {
-					/* We've exceed the stack rlimit. */
-					ret = -E2BIG;
-					goto out;
-				}
-#endif
-				ret = get_user_pages(current, bprm->mm, pos,
-						     1, 1, 1, &page, NULL);
-				if (ret <= 0) {
-					/* We've exceed the stack rlimit. */
+				page = get_arg_page(bprm, pos, 1);
+				if (!page) {
 					ret = -E2BIG;
 					goto out;
 				}
@@ -1604,8 +1604,10 @@ out:
 		security_bprm_free(bprm);
 
 out_mm:
-	if (bprm->mm)
+	if (bprm->mm) {
+		acct_arg_size(bprm, 0);
 		mmput(bprm->mm);
+	}
 
 out_file:
 	if (bprm->file) {
diff --git a/fs/exec.c b/fs/exec.c
index d6f4971..2b561ff 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -179,7 +179,7 @@ exit:
 
 #ifdef CONFIG_MMU
 
-static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
+void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 {
 	struct mm_struct *mm = current->mm;
 	long diff = (long)(pages - bprm->vma_pages);
@@ -306,7 +306,7 @@ static bool valid_arg_len(struct linux_binprm *bprm, long len)
 
 #else
 
-static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
+void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 {
 }
 
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index b05117c..d16b5b8 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -49,6 +49,10 @@ struct linux_binprm{
 #endif
 };
 
+extern void acct_arg_size(struct linux_binprm *bprm, unsigned long pages);
+extern struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
+					int write);
+
 #define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
 #define BINPRM_FLAGS_ENFORCE_NONDUMP (1 << BINPRM_FLAGS_ENFORCE_NONDUMP_BIT)