[PATCH] 6pack: fix buffer length mishandling
From: Alan <hidden>
Date: 2016-09-19 19:15:32
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 <redacted> --- drivers/net/hamradio/6pack.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 5a1e985..470b3dc 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c@@ -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 @@ static void sixpack_write_wakeup(struct tty_struct *tty) /* * 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;