[PATCH] Fix memory corruption in console selection

Mikulas Patocka
2009-01-30T20:27:32Z

[ I don't know who is the console maintainer or if there is any, so I'm
posting this to Linus ]

Fix an off-by-two memory error in console selection.

The loop below goes from sel_start to sel_end (inclusive), so it writes
one more character. This one more character was added to the allocated
size (+1), but it was not multiplied by an UTF-8 multiplier.

This patch fixes a memory corruption when UTF-8 console is used and the
user selects a few characters, all of them 3-byte in UTF-8 (for example a
frame line).

When memory redzones are enabled, a redzone corruption is reported. When
they are not enabled, trashing of random memory occurs.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
drivers/char/selection.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.29-rc3-devel/drivers/char/selection.c
===================================================================
--- linux-2.6.29-rc3-devel.orig/drivers/char/selection.c 2009-01-30 21:03:07.000000000 +0100
+++ linux-2.6.29-rc3-devel/drivers/char/selection.c 2009-01-30 21:03:38.000000000 +0100
@@ -268,7 +268,7 @@ int set_selection(const struct tiocl_sel

/* Allocate a new buffer before freeing the old one ... */
multiplier = use_unicode ? 3 : 1; /* chars can take up to 3 bytes */
- bp = kmalloc((sel_end-sel_start)/2*multiplier+1, GFP_KERNEL);
+ bp = kmalloc(((sel_end-sel_start)/2+1)*multiplier, GFP_KERNEL);
if (!bp) {
printk(KERN_WARNING "selection: kmalloc() failed\n");
clear_selection();