Package: coreutils
Version: 5.93-5
bug#339400 was closed prematurely...
> > notice that tail -f works fine when the file is not marked append only...
> > now don't ask me why O_NONBLOCK is denied on append only files... but it
> > is...
>
> I take it that there is no bug in the tail program, then.
there is absolutely a bug in the tail program... this was not a problem in
5.2.1-2.1 because the older version doesn't foolishly try to force
O_NONBLOCK on a regular file. the patch below fixes this problem.
append-only files are still readable -- they just can't be written
anywhere except at the end.
append-only are the ideal log file -- especially if they're being written
by a non-root user... for example, if a non-root user is compromised they
still can't modify log files to erase their tracks -- they have to make it
to root first and remove the append-only attribute.
considering tail -f worked on append-only files prior to 5.93 i consider
this to be a necessary fix...
-dean
p.s. i've reported this upstream, and i think the kernel is in error as
well, so i'm reporting it there too.
--- coreutils-5.93/src/tail.c.orig 2005-11-02 05:18:47.000000000 -0800
+++ coreutils-5.93/src/tail.c 2005-11-15 17:58:55.852102952 -0800
@@ -1020,7 +1020,8 @@
int new_flags = old_flags | (blocking ? 0 : O_NONBLOCK);
if (old_flags < 0
|| (new_flags != old_flags
- && fcntl (fd, F_SETFL, new_flags) == -1))
+ && fcntl (fd, F_SETFL, new_flags) == -1
+ && (!S_ISREG(f[i].mode) || errno != EPERM)))
error (EXIT_FAILURE, errno,
_("%s: cannot change nonblocking mode"), name);
f[i].blocking = blocking;
--
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