j...@wxcvbn.org (Jeremie Courreges-Anglas) writes:
> "Todd C. Miller" <todd.mil...@courtesan.com> writes:
>
>> From source inspection, Net and Free appear to allow read(2) of
>> dirs to succeed. However, since Linux, Mac OS X and Solaris have
>> the EISDIR behavior I think it is probably safe from a portability
>> standpoint.
>>
>> We're long past the days when opendir(3)/readdir(3) used read(2)...
>>
>> HP-UX and AIX still allow reads of directories but no one cares
>> about them ;-)
>
> So I think that we agree that EISDIR is more useful, and seems safe from
> a portability POV. I've built base and x sets on i386, and ajacoutot
> ran the ports bulk builds. The two offenders in the ports tree were due
> to an unrelated glitch in base libtool which has since been fixed.
I've hold this for a few days until the release cycle comes back to an
almost normal state. But, as Theo points out, we have to think about the
drawbacks. Some configurations that do work right now are very likely
to break.
$ cat /; echo $?
cat: /: Is a directory
1
is only a trivial example.
I still think that it is better to error out instead of, for example,
silently ignoring invalid/mistyped CLI arguments and config parameters.
But I don't want to mindlessly break people's setups behind their backs,
so I'd like to hear more opinions and... *test reports*.
Diff below for convenience.
Index: lib/libc/sys/read.2
===================================================================
RCS file: /cvs/src/lib/libc/sys/read.2,v
retrieving revision 1.35
diff -u -p -r1.35 read.2
--- lib/libc/sys/read.2 5 Feb 2015 02:33:09 -0000 1.35
+++ lib/libc/sys/read.2 9 Jul 2016 17:20:39 -0000
@@ -152,13 +152,15 @@ is not a valid file or socket descriptor
Part of
.Fa buf
points outside the process's allocated address space.
-.It Bq Er EIO
-An I/O error occurred while reading from the file system.
.It Bq Er EINTR
A read from a slow device
(i.e. one that might block for an arbitrary amount of time)
was interrupted by the delivery of a signal
before any data arrived.
+.It Bq Er EIO
+An I/O error occurred while reading from the file system.
+.It Bq Er EISDIR
+The underlying file is a directory.
.El
.Pp
In addition,
Index: sys/kern/vfs_vnops.c
===================================================================
RCS file: /cvs/src/sys/kern/vfs_vnops.c,v
retrieving revision 1.85
diff -u -p -r1.85 vfs_vnops.c
--- sys/kern/vfs_vnops.c 19 Jun 2016 11:54:33 -0000 1.85
+++ sys/kern/vfs_vnops.c 9 Jul 2016 17:20:39 -0000
@@ -336,11 +336,13 @@ vn_read(struct file *fp, off_t *poff, st
if (vp->v_type != VCHR && count > LLONG_MAX - *poff)
return (EINVAL);
+ if (vp->v_type == VDIR)
+ return (EISDIR);
+
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
uio->uio_offset = *poff;
- if (vp->v_type != VDIR)
- error = VOP_READ(vp, uio,
- (fp->f_flag & FNONBLOCK) ? IO_NDELAY : 0, cred);
+ error = VOP_READ(vp, uio, (fp->f_flag & FNONBLOCK) ? IO_NDELAY : 0,
+ cred);
*poff += count - uio->uio_resid;
VOP_UNLOCK(vp, p);
return (error);
--
jca | PGP: 0x1524E7EE / 5135 92C1 AD36 5293 2BDF DDCC 0DFA 74AE 1524 E7EE
