From 690dbe1ced143876d8fa56b72310738dbe079d0a Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hugh@veritas.com>
Date: Mon, 1 Aug 2005 21:11:42 -0700
Subject: [PATCH] [PATCH] x86_64: access of some bad address
x86_64 has a large sparse gate area between VSYSCALL_START and
VSYSCALL_END, not all of it presently backed by pmds. Alexander Nyberg has
found that in some circumstances gdb may try to ptrace here, and hit
get_user_pages BUG_ON. It seems odd that gdb should be accessing here, but
it certainly shouldn't crash in this way: relax BUG_ON to -EFAULT. Fixes
kernel bugzilla #4801.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
mm/memory.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 4e1c673784dbb..2405289dfdf88 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -910,9 +910,13 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
pud = pud_offset(pgd, pg);
BUG_ON(pud_none(*pud));
pmd = pmd_offset(pud, pg);
- BUG_ON(pmd_none(*pmd));
+ if (pmd_none(*pmd))
+ return i ? : -EFAULT;
pte = pte_offset_map(pmd, pg);
- BUG_ON(pte_none(*pte));
+ if (pte_none(*pte)) {
+ pte_unmap(pte);
+ return i ? : -EFAULT;
+ }
if (pages) {
pages[i] = pte_page(*pte);
get_page(pages[i]);
--
GitLab