From: Nick Alcock <nick.alcock@oracle.com>
Date: Mon, 31 Oct 2016 10:44:26 +0000 (+0000)
Subject: dtrace: take mmap_sem in PTRACE_GETMAPFD
X-Git-Tag: v4.1.12-92~25^2~7
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c5e8c2137267addd66d214f0c7b986793cedf0af;p=users%2Fjedix%2Flinux-maple.git

dtrace: take mmap_sem in PTRACE_GETMAPFD

Without this, we may oops if the process exec()s and discards its
address space after we find_vma().

Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Acked-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Orabug: 24977175
---

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 5c511f403e42a..10467305c8eb3 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -815,6 +815,7 @@ static int ptrace_getmapfd(struct task_struct *child, unsigned long addr,
 
 	mm = get_task_mm(child);
 	files = get_files_struct(child);
+	down_read(&mm->mmap_sem);
 	vma = find_vma(mm, addr);
 
 	if (!vma || vma->vm_start > addr) {
@@ -838,6 +839,7 @@ static int ptrace_getmapfd(struct task_struct *child, unsigned long addr,
 	fd_install(new_fd, vma->vm_file);
 
 err:
+	up_read(&mm->mmap_sem);
 	put_files_struct(files);
 	mmput(mm);