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Fix the calculations of the length of the unread message buffer

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contents. The code was subtracting two unsigned ints, stored the
result in a log and expected it to be the same as of a signed
subtraction; this does only work on platforms where int and long
have the same size (due to overflows).
Instead, cast to long before the subtraction; the numbers are
guaranteed to be small enough so that there will be no overflows
because of that.
This commit is contained in:
Thomas Moestl 2002-10-20 23:13:05 +00:00
parent 72d26fe4c9
commit 5775150869
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=105590
1 changed files with 2 additions and 2 deletions
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4
sys/kern/subr_log.c
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@ -147,7 +147,7 @@ logread(dev_t dev, struct uio *uio, int flag)
logsoftc.sc_state &= ~LOG_RDWAIT;
while (uio->uio_resid > 0) {
l = mbp->msg_bufx - mbp->msg_bufr;
l = (long)mbp->msg_bufx - mbp->msg_bufr;
if (l < 0)
l = mbp->msg_size - mbp->msg_bufr;
l = min(l, uio->uio_resid);
@ -218,7 +218,7 @@ logioctl(dev_t dev, u_long com, caddr_t data, int flag, struct thread *td)
/* return number of characters immediately available */
case FIONREAD:
s = splhigh();
l = msgbufp->msg_bufx - msgbufp->msg_bufr;
l = (long)msgbufp->msg_bufx - msgbufp->msg_bufr;
splx(s);
if (l < 0)
l += msgbufp->msg_size;