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Bug#35695: marked as done (libc6: ttyname() broken ?)

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From: Madarasz Gergely <gorgo@thunderchild.aszi.sztaki.hu>
Subject: libc6: ttyname() broken ?
To: submit@bugs.debian.org
X-Mailer: bug 3.1.7
Message-Id: <E10UuPa-0000jc-00@thunderchild.aszi.sztaki.hu>
Date: Wed, 7 Apr 1999 17:38:42 +0200

Package: libc6
Version: 2.1.1-0.1

After upgrading to kernel 2.2.5-ac4, screen does not work. It seems to be a
problem with glibc. Here are the facts:

# screen
Cannot access '/dev/ptsÿÿÿÿÿÿÿÿ': No such file or directory

ltracing it reveals the following:
ttyname(0)                                        = "/dev/pts/0\b\bEOFEOFEOFEOFEOFEOFEOFEOF"
__xstat(3, "/dev/pts/0\b\bEOFEOFEOFEOFEOFEOFEOFEOF", 0xbfffe930) = -1

If I strace it, it says the following:
readlink("/proc/self/fd/0", "/dev/pts/0", 4095) = 10
stat("/dev/pts/^H<FF><FF><FF><FF><FF><FF><FF><FF>", 0xbfffe7d0) = -1 ENOENT
(No such file or directory)

See the return value of readlink. On a non-ac kernel it returns 11,
terminating the string with a \0. Here is the relevant part of the patch of 
the ac kernel:

--- linux.vanilla/fs/proc/link.c        Sun Nov  8 15:06:32 1998
+++ linux.ac/fs/proc/link.c     Wed Mar 24 18:14:32 1999
@@ -158,7 +158,7 @@
                path = tmp;
        } else {
                path = d_path(dentry, tmp, PAGE_SIZE);
-               len = tmp + PAGE_SIZE - path;
+               len = tmp + PAGE_SIZE - 1 - path;

        if (len < buflen)

Reading the manpage of readlink() it seems that this patch is correct, and
readlink should not terminate the string with a \0:

       readlink  places the contents of the symbolic link path in
       the buffer buf, which has size bufsiz.  readlink does  not
       append  a NUL character to buf...

       The  call  returns  the  count of characters placed in the
       buffer if it succeeds, or a -1 if an error occurs, placing
       the error code in errno.

In this case the ttyname() function of libc should take care of terminating
the string with \0 before returning it to the caller.

-- System Information
Debian Release: potato
Kernel Version: Linux thunderchild 2.2.5 #2 Fri Apr 2 15:44:43 CEST 1999 i586 unknown

Versions of the packages libc6 depends on:
ii  ldso            1.9.10-1.2     The Linux dynamic linker, library and utilit

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