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6pack: fix buffer length mishandling 

Dmitry Vyukov wrote:
> different runs). Looking at code, the following looks suspicious -- we
> limit copy by 512 bytes, but use the original count which can be
> larger than 512:
>
> static void sixpack_receive_buf(struct tty_struct *tty,
>     const unsigned char *cp, char *fp, int count)
> {
>     unsigned char buf[512];
>     ....
>     memcpy(buf, cp, count < sizeof(buf) ? count : sizeof(buf));
>     ....
>     sixpack_decode(sp, buf, count1);

With the sane tty locking we now have I believe the following is safe as
we consume the bytes and move them into the decoded buffer before
returning.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alan Cox 2016-09-19 20:15:24 +01:00 committed by David S. Miller
parent 5737f6c926
commit ad9798967d
1 changed files with 4 additions and 8 deletions
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12
drivers/net/hamradio/6pack.c
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@ -127,7 +127,7 @@ struct sixpack {
#define AX25_6PACK_HEADER_LEN 0
static void sixpack_decode(struct sixpack *, unsigned char[], int);
static void sixpack_decode(struct sixpack *, const unsigned char[], int);
static int encode_sixpack(unsigned char *, unsigned char *, int, unsigned char);
/*
@ -428,7 +428,7 @@ out:
/*
* Handle the 'receiver data ready' interrupt.
* This function is called by the 'tty_io' module in the kernel when
* This function is called by the tty module in the kernel when
* a block of 6pack data has been received, which can now be decapsulated
* and sent on to some IP layer for further processing.
*/
@ -436,7 +436,6 @@ static void sixpack_receive_buf(struct tty_struct *tty,
const unsigned char *cp, char *fp, int count)
{
struct sixpack *sp;
unsigned char buf[512];
int count1;
if (!count)
@ -446,10 +445,7 @@ static void sixpack_receive_buf(struct tty_struct *tty,
if (!sp)
return;
memcpy(buf, cp, count < sizeof(buf) ? count : sizeof(buf));
/* Read the characters out of the buffer */
count1 = count;
while (count) {
count--;
@ -459,7 +455,7 @@ static void sixpack_receive_buf(struct tty_struct *tty,
continue;
}
}
sixpack_decode(sp, buf, count1);
sixpack_decode(sp, cp, count1);
sp_put(sp);
tty_unthrottle(tty);
@ -992,7 +988,7 @@ static void decode_std_command(struct sixpack *sp, unsigned char cmd)
/* decode a 6pack packet */
static void
sixpack_decode(struct sixpack *sp, unsigned char *pre_rbuff, int count)
sixpack_decode(struct sixpack *sp, const unsigned char *pre_rbuff, int count)
{
unsigned char inbyte;
int count1;