Debian Bug report logs - #20426
realpath(3) can't deal with circular symlinks

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Peter Tobias <tobias@et-inf.fho-emden.de>

To: submit@bugs.debian.org

Subject: man-db: mandb can't deal with circular symlinks

Date: Mon, 30 Mar 1998 03:43:30 +0200

Package: man-db
Version: 2.3.10-64

mandb --create dies with a segmentation fault when it tries to follow
a cirular symbolic link.

# ls -l /usr/man/man1/uudecode.1.gz /etc/alternatives/uudecode.1.gz
lrwxrwxrwx   1 root     root           27 Mar  2 11:44 /etc/alternatives/uudecode.1.gz -> /usr/man/man1/uudecode.1.gz
lrwxrwxrwx   1 root     root           31 Nov 24 05:26 /usr/man/man1/uudecode.1.gz -> /etc/alternatives/uudecode.1.gz


Thanks,

Peter

-- 
Peter Tobias <tobias@et-inf.fho-emden.de> <tobias@debian.org> <tobias@linux.de>
PGP ID EFAA400D, fingerprint = 06 89 EB 2E 01 7C B4 02  04 62 89 6C 2F DD F1 3C 

Message #10 received at 20426@bugs.debian.org (full text, mbox, reply):

From: fpolacco@icenet.fi

To: Peter Tobias <tobias@et-inf.fho-emden.de>, 20426@bugs.debian.org, control@bugs.debian.org

Subject: Re: Bug#20426: man-db: mandb can't deal with circular symlinks

Date: Thu, 2 Apr 1998 17:28:13 +0300

reassign 20426 libc6
retitle 20426 realpath(3) can't deal with circular symlinks
stop

On Mon, Mar 30, 1998 at 03:43:30AM +0200, Peter Tobias wrote:
> Package: man-db
> Version: 2.3.10-64
> 
> mandb --create dies with a segmentation fault when it tries to follow
> a cirular symbolic link.
> 

You're right, thank you for the report.
I've spent some hours debugging the "thing" on my slow 486, and I found ...
that I can do nothing.
The program calls realpath(3) which never returns, entering a loop which calls
canonicalize tons of times, allocating memory at line 124
              char *buf = __alloca (path_max);

ending in a segfault at line 132
(gdb) p buf
$3 = 0xbf7ffedc <Address 0xbf7ffedc out of bounds>


I have to reassign this bug to libc6 (sorry Dale); in fact, you get the same
segfault issuing the command  realpath(1) (in dwww, by LarsW.) with the
circular symlink as argument.

$ ls -la /etc/alternatives/uurecode.1.gz /usr/man/man1/uurecode.1.gz 
lrwxrwxrwx  27 Apr  2 10:19 /etc/alternatives/uurecode.1.gz -> /usr/man/man1/uurecode.1.gz
lrwxrwxrwx  31 Apr  2 10:19 /usr/man/man1/uurecode.1.gz -> /etc/alternatives/uurecode.1.gz

$ realpath /usr/man/man1/uurecode.1.gz 
Segmentation fault (core dumped)

$ ls -la core
-rw-------   1 fab      fab       8482816 Apr  2 17:21 core


Sorry for having to leave a segfault unsolved, but I don't know how to modify
glibc to make it avoid the loop in case of circular symlinks.

fab
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