Re: [libvirt] [PATCH] util: Don't overflow on errno in virFileAccessibleAs

On 03/08/2012 03:37 AM, Michal Privoznik wrote: > If we need to virFork() to check assess() under different > UID+GID we need to translate returned status via WEXITSTATUS(). > Otherwise, we may return values greater than 255 which is > obviously wrong. > --- > src/util/util.c | 7 ++++++- > 1 files changed, 6 insertions(+), 1 deletions(-) > > diff --git a/src/util/util.c b/src/util/util.c > index 548ed1c..15e6cfa 100644 > --- a/src/util/util.c > +++ b/src/util/util.c > @@ -724,8 +724,13 @@ virFileAccessibleAs(const char *path, int mode, > return -1; > } > > + if (!WIFEXITED(status)) { > + errno = EINTR; > + return -1; > + } ACK; this matches what we do in virFileOpenForked.

However, I still see two lingering issues that might be worth revisiting: 1. I wonder if virWaitPid() would be easier to use if it only returned success on WIFEXITED, and set *status to WEXITSTAUS(), while returning -1 on any child dying due to a signal. I'd have to audit the users of virWaitPid to see if they can all be simplified by this change, or if there really is a user that needs to know if a child exited due to a signal.

2. This still shares the latent bug in virFileOpenForked that errno is not always guaranteed to be less than 255; on GNU Hurd, this code is broken - but libvirt doesn't compile on Hurd. A true fix would be to enumerate specific errno values to specific exit codes, and map all others to a catch-all; see how daemon/libvirtd.c has virDaemonErr for this purpose.