[PATCH 1/2] drivers/serial/icom.c: Eliminate use after free

From: Julia Lawall
Date: Fri Jul 30 2010 - 11:17:13 EST

From: Julia Lawall <julia@xxxxxxx>

Release_firmware has two definitions, one of which does nothing
(include/linux/firmware.h) and one of which always frees its argument
(drivers/base/firmware_class.c). If the latter can be used, the access to
the size field inthe argument of writeb represents a use after free. The
patch thus saves the size value before calling release_firmware and then
uses it afterwards.

A simplified version of the semantic patch that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
expression E,E2;

E = E2
* E
// </smpl>

Signed-off-by: Julia Lawall <julia@xxxxxxx>

Another possibility would be to put the call to remove_firmware later. One
could also wonder whether the first argument to writeb could be calculated
using DIV_ROUND_UP, even though the semantics is not exactly the same.

drivers/serial/icom.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/icom.c b/drivers/serial/icom.c
index 53a4682..f82e95a 100644
--- a/drivers/serial/icom.c
+++ b/drivers/serial/icom.c
@@ -360,6 +360,7 @@ static void load_code(struct icom_port *icom_port)
unsigned char *new_page = NULL;
unsigned char cable_id = NO_CABLE;
struct pci_dev *dev = icom_port->adapter->pci_dev;
+ size_t size;

/* Clear out any pending interrupts */
writew(0x3FFF, icom_port->int_reg);
@@ -454,9 +455,10 @@ static void load_code(struct icom_port *icom_port)
for (index = 0; index < fw->size; index++)
new_page[index] = fw->data[index];

+ size = fw->size;

- writeb((char) ((fw->size + 16)/16), &icom_port->dram->mac_length);
+ writeb((char) ((size + 16)/16), &icom_port->dram->mac_length);
writel(temp_pci, &icom_port->dram->mac_load_addr);

/*Setting the syncReg to 0x80 causes adapter to start downloading
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