Re: [libvirt] [PATCH] avoid a probable EINVAL from lseek
Daniel P. Berrange wrote:
On Mon, Feb 01, 2010 at 10:18:27PM +0100, Jim Meyering wrote:
>
> In src/qemu/qemu_driver.c, coverity reports this:
>
> Event negative_return_fn: Called negative-returning function "lseek(logfile,
0L, 2)"
> Event var_assign: NEGATIVE return value of "lseek" assigned to signed
variable "pos"
> At conditional (1): "(pos = lseek(logfile, 0L, 2)) < 0" taking true
path
> 2877 if ((pos = lseek(logfile, 0, SEEK_END)) < 0)
> 2878 VIR_WARN(_("Unable to seek to end of logfile: %s"),
> 2879 virStrerror(errno, ebuf, sizeof ebuf));
I think it'd be less surprising to just set 'pos = 0' inside the if
branch here, so later code doesn't have to worry about unexpected
negative values.
Oh. I pushed after DV's ACK.
That would let the later code continue, but using (lseek'ing to) an
invalid position. Sounds like it could result in a cascade of
additional errors, or worse, silent malfunction.
But this is largely hypothetical, since failing to lseek-to-EOF
on a valid file descriptor is not likely to happen.
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 22593bf..676a27b 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -558,8 +558,8 @@ qemudLogReadFD(virConnectPtr conn, const char* logDir, const
char* name, off_t p
> close(fd);
> return -1;
> }
> - if (lseek(fd, pos, SEEK_SET) < 0) {
> - virReportSystemError(conn, errno,
> + if (pos < 0 || lseek(fd, pos, SEEK_SET) < 0) {
> + virReportSystemError(conn, pos < 0 ? 0 : errno,
> _("Unable to seek to %lld in %s"),
> (long long) pos, logfile);
> close(fd);