Re: [PATCH] Fix NR_KEYS off-by-one error

OGAWA Hirofumi
2004-07-28T16:48:30Z

Andries Brouwer <aebr@win.tue.nl> writes:

> When an array has an arbitrary upper bound that can be changed
> via a #define, and for some values of the upper bound a test
> is superfluous, that does not mean that the test is superfluous.

OK. The patch is the following.

Any comments or suggestions?
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

[PATCH] Fix NR_KEYS off-by-one error

KDGKBENT ioctl can use 256 entries (0-255), but it was defined as
key_map[NR_KEYS] (NR_KEYS == 255). The code seems also thinking it's 256.

key_map[0] = U(K_ALLOCATED);
for (j = 1; j < NR_KEYS; j++)
key_map[j] = U(K_HOLE);

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---

drivers/char/vt_ioctl.c | 6 ++++++
include/linux/keyboard.h | 2 +-
2 files changed, 7 insertions(+), 1 deletion(-)

diff -puN include/linux/keyboard.h~nr_keys-off-by-one include/linux/keyboard.h
--- linux-2.6.8-rc2/include/linux/keyboard.h~nr_keys-off-by-one 2004-07-28 03:37:12.000000000 +0900
+++ linux-2.6.8-rc2-hirofumi/include/linux/keyboard.h 2004-07-28 03:37:12.000000000 +0900
@@ -16,7 +16,7 @@

#define NR_SHIFT 9

-#define NR_KEYS 255
+#define NR_KEYS 256
#define MAX_NR_KEYMAPS 256
/* This means 128Kb if all keymaps are allocated. Only the superuser
may increase the number of keymaps beyond MAX_NR_OF_USER_KEYMAPS. */
diff -puN drivers/char/vt_ioctl.c~nr_keys-off-by-one drivers/char/vt_ioctl.c
--- linux-2.6.8-rc2/drivers/char/vt_ioctl.c~nr_keys-off-by-one 2004-07-29 01:31:12.000000000 +0900
+++ linux-2.6.8-rc2-hirofumi/drivers/char/vt_ioctl.c 2004-07-29 01:35:23.000000000 +0900
@@ -83,6 +83,12 @@ do_kdsk_ioctl(int cmd, struct kbentry __
if (copy_from_user(&tmp, user_kbe, sizeof(struct kbentry)))
return -EFAULT;

+#if NR_KEYS != 256 || MAX_NR_KEYMAPS != 256
+#error "you should check this too"
+ if (i >= NR_KEYS || s >= MAX_NR_KEYMAPS)
+ return -EINVAL;
+#endif
+
switch (cmd) {
case KDGKBENT:
key_map = key_maps[s];
_