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Apply the PG_sensitive flag to the tty API

PATCH In review Larry H. 1 participant 1 message May 20, 2009

Subsystems (2)
Memory management Char and misc drivers
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Larry H.

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#0 lore raw

PATCH 1/5 Apply the PG_sensitive flag to the tty API

This patch deploys the use of the PG_sensitive page allocator flag within the tty API, in the buffer management, input event handling and input auditing code.

This should provide an additional safety layer against tty buffers leaking information including passwords and other likely sensitive input.

Again, you might refer to the paper by Jim Chow et. al on reducing data resilience through secure deallocation. It explicitly mentions this case, as well as other scenarios [1].

[1] http://www.stanford.edu/~blp/papers/shredding.html

Signed-off-by Larry H. <[email protected]>
---
 drivers/char/tty_audit.c  |    6 +++---
 drivers/char/tty_buffer.c |    2 +-
 drivers/char/tty_io.c     |    2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)
drivers/char/tty_audit.c +3 -3
Index: linux-2.6/drivers/char/tty_audit.c
===================================================================
@@ -28,13 +28,13 @@ static struct tty_audit_buf *tty_audit_b
 {
 	struct tty_audit_buf *buf;
 
-	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
+	buf = kmalloc(sizeof(*buf), GFP_KERNEL | GFP_SENSITIVE);
 	if (!buf)
 		goto err;
 	if (PAGE_SIZE != N_TTY_BUF_SIZE)
-		buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
+		buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL | GFP_SENSITIVE);
 	else
-		buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
+		buf->data = (unsigned char *)__get_free_page(GFP_KERNEL | GFP_SENSITIVE);
 	if (!buf->data)
 		goto err_buf;
 	atomic_set(&buf->count, 1);
drivers/char/tty_buffer.c +1 -1
Index: linux-2.6/drivers/char/tty_buffer.c
===================================================================
@@ -60,7 +60,7 @@ static struct tty_buffer *tty_buffer_all
 
 	if (tty->buf.memory_used + size > 65536)
 		return NULL;
-	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
+	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC | GFP_SENSITIVE);
 	if (p == NULL)
 		return NULL;
 	p->used = 0;
drivers/char/tty_io.c +1 -1
Index: linux-2.6/drivers/char/tty_io.c
===================================================================
@@ -1031,7 +1031,7 @@ static inline ssize_t do_tty_write(
 		if (chunk < 1024)
 			chunk = 1024;
 
-		buf_chunk = kmalloc(chunk, GFP_KERNEL);
+		buf_chunk = kmalloc(chunk, GFP_KERNEL | GFP_SENSITIVE);
 		if (!buf_chunk) {
 			ret = -ENOMEM;
 			goto out;

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