On 28/05/10 14:17, Pádraig Brady wrote:
>> what about --ref=non-regular-file ?
>>
>> Perhaps truncate should refuse to use st_size info from
>> a non-regular file.
>>
>> Here's a pathological example:
>>
>> $ echo abcdefgh > bar
>> $ strace -e ftruncate ./truncate --ref=/dev/tty bar
>> ftruncate(3, 0) = 0
>> $ wc -c bar
>> 0 bar
>>
>> It's obvious that such an example is not likely in practice, but since
>> currently truncate's --ref uses stat, it would follow a symlink, too.
>>
>> For a directory you'd get unportable and probably surprising results.
>> Using such a reference size deserves at least a warning.
>
> Yes that's safer. st_size is only defined for regular files
> (or shared mem), so I'll only allow regular files.
> I'll push a separate patch soon.
>
> Since we're only referencing the size, there is the argument
> that we should be trying harder to get the size of block devices
> for example. There are portability issues with that though,
> and doing outside of truncate is easy enough, so I'll leave that for now.
I actually removed all ignoring of errors for
non regular files, as well as not allowing
one to reference st_size for non regular files.
I'll push the attached tomorrow sometime.
cheers,
Pádraig.
>From 0b9588c10cb3783ade69892302eb0d1379866af6 Mon Sep 17 00:00:00 2001
From: =?utf-8?q?P=C3=A1draig=20Brady?= <p...@draigbrady.com>
Date: Fri, 28 May 2010 19:25:23 +0100
Subject: [PATCH] truncate: improve handling of non regular files
Previously we copied `dd` and suppressed error messages
when truncating neither regular files or shared mem objects.
This was valid for `dd`, as truncation is ancillary to copying
it may also do, but for `truncate` we should display all errors.
Also we used the st_size from non regular files which is undefined,
so we display an error when the user tries this.
* src/truncate (do_truncate): Error when referencing the size
of non regular files or non shared memory objects. Display all
errors returned by ftruncate().
(main): Error when referencing the size of non regular files or
non shared memory objects. Don't suppress error messages for
any file types that can't be opened for writing.
* tests/misc/truncate-dir-fail: Check that referencing the
size of a directory is not supported.
* tests/misc/truncate-fifo: Ensure the test doesn't hang
by using the `timeout` command. Don't test the return from
running ftruncate on the fifo as it's system dependent as
to whether this fails or not.
---
src/truncate.c | 59 +++++++++++++-----------------------------
tests/misc/truncate-dir-fail | 3 ++
tests/misc/truncate-fifo | 6 ++--
3 files changed, 24 insertions(+), 44 deletions(-)
diff --git a/src/truncate.c b/src/truncate.c
index 08090ab..cfb5747 100644
--- a/src/truncate.c
+++ b/src/truncate.c
@@ -160,21 +160,21 @@ do_ftruncate (int fd, char const *fname, off_t ssize, off_t rsize,
{
uintmax_t const fsize = rsize < 0 ? sb.st_size : rsize;
- if (rsize < 0 && sb.st_size < 0)
+ if (rsize < 0) /* fstat used above to get size. */
{
- /* Complain only for a regular file, a directory,
- or a shared memory object, as POSIX 1003.1-2004 specifies
- ftruncate's behavior only for these file types. */
- if (S_ISREG (sb.st_mode) || S_ISDIR (sb.st_mode)
- || S_TYPEISSHM (&sb))
+ if (!S_ISREG (sb.st_mode) && !S_TYPEISSHM (&sb))
{
- /* overflow is the only reason I can think
- this would ever go negative for the above types */
+ error (0, 0, _("cannot get the size of %s"), quote (fname));
+ return 1;
+ }
+ if (sb.st_size < 0)
+ {
+ /* Sanity check. Overflow is the only reason I can think
+ this would ever go negative. */
error (0, 0, _("%s has unusable, apparently negative size"),
quote (fname));
return 1;
}
- return 0;
}
if (rel_mode == rm_min)
@@ -215,26 +215,10 @@ do_ftruncate (int fd, char const *fname, off_t ssize, off_t rsize,
if (ftruncate (fd, nsize) == -1) /* note updates mtime & ctime */
{
- /* Complain only when ftruncate fails on a regular file, a
- directory, or a shared memory object, as POSIX 1003.1-2004
- specifies ftruncate's behavior only for these file types.
- For example, do not complain when Linux kernel 2.4 ftruncate
- fails on /dev/fd0. */
- int const ftruncate_errno = errno;
- if (fstat (fd, &sb) != 0)
- {
- error (0, errno, _("cannot fstat %s"), quote (fname));
- return 1;
- }
- else if (S_ISREG (sb.st_mode) || S_ISDIR (sb.st_mode)
- || S_TYPEISSHM (&sb))
- {
- error (0, ftruncate_errno,
- _("truncating %s at %" PRIdMAX " bytes"), quote (fname),
- (intmax_t) nsize);
- return 1;
- }
- return 0;
+ error (0, errno,
+ _("truncating %s at %" PRIdMAX " bytes"), quote (fname),
+ (intmax_t) nsize);
+ return 1;
}
return 0;
@@ -362,9 +346,13 @@ main (int argc, char **argv)
if (ref_file)
{
+ /* FIXME: Maybe support getting size of block devices. */
struct stat sb;
if (stat (ref_file, &sb) != 0)
error (EXIT_FAILURE, errno, _("cannot stat %s"), quote (ref_file));
+ if (!S_ISREG (sb.st_mode) && !S_TYPEISSHM (&sb))
+ error (EXIT_FAILURE, 0, _("cannot get the size of %s"),
+ quote (ref_file));
if (!got_size)
size = sb.st_size;
else
@@ -384,18 +372,7 @@ main (int argc, char **argv)
`truncate -s0 .` should gen EISDIR error */
if (!(no_create && errno == ENOENT))
{
- int const open_errno = errno;
- struct stat sb;
- if (stat (fname, &sb) == 0)
- {
- /* Complain only for a regular file, a directory,
- or a shared memory object, as POSIX 1003.1-2004 specifies
- ftruncate's behavior only for these file types. */
- if (!S_ISREG (sb.st_mode) && !S_ISDIR (sb.st_mode)
- && !S_TYPEISSHM (&sb))
- continue;
- }
- error (0, open_errno, _("cannot open %s for writing"),
+ error (0, errno, _("cannot open %s for writing"),
quote (fname));
errors++;
}
diff --git a/tests/misc/truncate-dir-fail b/tests/misc/truncate-dir-fail
index d2ecf2f..fe33857 100755
--- a/tests/misc/truncate-dir-fail
+++ b/tests/misc/truncate-dir-fail
@@ -26,4 +26,7 @@ fi
# truncate on dir not allowed
truncate -s+0 . && fail=1
+# getting the size of a dir is not allowed
+truncate -r. file && fail=1
+
Exit $fail
diff --git a/tests/misc/truncate-fifo b/tests/misc/truncate-fifo
index 8e2276d..12d674c 100755
--- a/tests/misc/truncate-fifo
+++ b/tests/misc/truncate-fifo
@@ -1,5 +1,5 @@
#!/bin/sh
-# Make sure truncate works on fifos without hanging or errors
+# Make sure truncate works on fifos without hanging
# Copyright (C) 2008-2010 Free Software Foundation, Inc.
@@ -25,7 +25,7 @@ fi
mkfifo_or_skip_ "fifo"
-
-truncate -s0 "fifo" || fail=1
+timeout 10 truncate -s0 "fifo"
+test "$?" = 124 && fail=1
Exit $fail
--
1.6.2.5
