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vt: keyboard, simplify vt_kdgkbsent 

commit 6ca03f9052 upstream.

Use 'strlen' of the string, add one for NUL terminator and simply do
'copy_to_user' instead of the explicit 'for' loop. This makes the
KDGKBSENT case more compact.

The only thing we need to take care about is NULL 'func_table[i]'. Use
an empty string in that case.

The original check for overflow could never trigger as the func_buf
strings are always shorter or equal to 'struct kbsentry's.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20201019085517.10176-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Jiri Slaby 2020-10-19 10:55:16 +02:00 committed by Greg Kroah-Hartman
parent 8c16ca6006
commit eb4c460e2e
1 changed files with 9 additions and 19 deletions
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28
drivers/tty/vt/keyboard.c
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@ -1994,9 +1994,7 @@ out:
int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
{
struct kbsentry *kbs;
char *p;
u_char *q;
u_char __user *up;
int sz, fnw_sz;
int delta;
char *first_free, *fj, *fnw;
@ -2022,23 +2020,15 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
i = kbs->kb_func;
switch (cmd) {
case KDGKBSENT:
sz = sizeof(kbs->kb_string) - 1; /* sz should have been
a struct member */
up = user_kdgkb->kb_string;
p = func_table[i];
if(p)
for ( ; *p && sz; p++, sz--)
if (put_user(*p, up++)) {
ret = -EFAULT;
goto reterr;
}
if (put_user('\0', up)) {
ret = -EFAULT;
goto reterr;
}
kfree(kbs);
return ((p && *p) ? -EOVERFLOW : 0);
case KDGKBSENT: {
/* size should have been a struct member */
unsigned char *from = func_table[i] ? : "";
ret = copy_to_user(user_kdgkb->kb_string, from,
strlen(from) + 1) ? -EFAULT : 0;
goto reterr;
}
case KDSKBSENT:
if (!perm) {
ret = -EPERM;