Messages in this thread | | | Date | Sun, 14 May 2006 18:18:46 +0400 | From | Alexey Dobriyan <> | Subject | Re: [PATCH] fix dangerous pointer derefs and remove pointless casts in MOXA driver |
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On Sun, May 14, 2006 at 03:49:35AM +0200, Jesper Juhl wrote: > If mxser_write() gets called with a NULL 'tty' pointer, then the initial > assignment of tty->driver_data to info will explode.
->write() is called via
tty->driver->write(tty, ...);
See? tty was already dereferenced.
> 'tty' is tested for NULL at the beginning of the function, but at that > point it is too late. > Fix the problem by only dereferencing tty after it has been tested. > > In mxser_put_char() there's the same problem with the same fix. > > This should fix coverity bugs #770 && #771 .
> --- linux-2.6.17-rc4-git2-orig/drivers/char/mxser.c > +++ linux-2.6.17-rc4-git2/drivers/char/mxser.c > @@ -877,7 +877,7 @@ static int mxser_init(void) > > static void mxser_do_softint(void *private_) > { > - struct mxser_struct *info = (struct mxser_struct *) private_; > + struct mxser_struct *info = private_;
Please, don't make unrelated changes, ever.
> struct tty_struct *tty; > > tty = info->tty;
> @@ -1078,11 +1077,15 @@ static void mxser_close(struct tty_struc > static int mxser_write(struct tty_struct *tty, const unsigned char *buf, int count) > { > int c, total = 0; > - struct mxser_struct *info = (struct mxser_struct *) tty->driver_data; > + struct mxser_struct *info; > unsigned long flags; > > - if (!tty || !info->xmit_buf) > - return (0); > + if (!tty) > + return 0; > + > + info = tty->driver_data; > + if (!info->xmit_buf) > + return 0; > > while (1) { > c = min_t(int, count, min(SERIAL_XMIT_SIZE - info->xmit_cnt - 1, SERIAL_XMIT_SIZE - info->xmit_head)); > @@ -1114,10 +1117,14 @@ static int mxser_write(struct tty_struct > > static void mxser_put_char(struct tty_struct *tty, unsigned char ch) > { > - struct mxser_struct *info = (struct mxser_struct *) tty->driver_data; > + struct mxser_struct *info; > unsigned long flags; > > - if (!tty || !info->xmit_buf) > + if (!tty) > + return; > + > + info = tty->driver_data; > + if (!info->xmit_buf) > return; > > if (info->xmit_cnt >= SERIAL_XMIT_SIZE - 1)
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