[PATCH 09/12] proc: disable mem_write after exec

[Stephen Wilson]

This change makes mem_write() observe the same constraints as mem_read().  This
is particularly important for mem_write as an accidental leak of the fd across
an exec could result in arbitrary modification of the target process' memory.
IOW, /proc/pid/mem is implicitly close-on-exec.

Signed-off-by: Stephen Wilson <wilsons@xxxxxxxx>
---
 fs/proc/base.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 9d096e8..e52702d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -848,6 +848,10 @@ static ssize_t mem_write(struct file * file, const char __user *buf,
 	if (check_mem_permission(task))
 		goto out;
 
+	copied = -EIO;
+	if (file->private_data != (void *)((long)current->self_exec_id))
+		goto out;
+
 	copied = -ENOMEM;
 	page = (char *)__get_free_page(GFP_TEMPORARY);
 	if (!page)
-- 
1.7.3.5

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