* execve for script don't return ENOEXEC, bug ?
@ 2010-03-11 10:56 Valery Reznic
2010-03-19 21:07 ` Andrew Morton
0 siblings, 1 reply; 10+ messages in thread
From: Valery Reznic @ 2010-03-11 10:56 UTC (permalink / raw)
To: linux-kernel
Hi,
I Have following to scripts:
a.sh
#!/bin/sh
echo "It's a.sh
and b.sh:
#! ./b.sh
echo "It's b.sh"
As per execve man page, script interpreter should not be script itself.
When I run it on my Fedora 8 x86_64 box (with stock kernel, never updated)
under strace I got following:
strace -f -e execve setarch x86_64 ./b.sh
execve("/usr/bin/setarch", ["setarch", "x86_64", "./b.sh"], [/* 23 vars */]) = 0
execve("./b.sh", ["./b.sh"], [/* 23 vars */]) = -1 ENOEXEC (Exec format error)
execve("/bin/sh", ["/bin/sh", "./b.sh"], [/* 23 vars */]) = 0
It's b.sh
I.e execve failed as it should
When I run same scripts on Fedora 12 x86_64 box with stock kernel 2.6.31.5-127.fc12.x86_64 I got following:
strace -f -e execve setarch i386 ./b.sh
execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"], [/* 41 vars */]) = 0
execve("./b.sh", ["./b.sh"], [/* 41 vars */]) = 0
It's a.sh
I.e execve succeeded, instead of failing with ENOEXEC
Regards,
Valery.
P.S. I am not subscribed to this list, so please CC me
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-11 10:56 execve for script don't return ENOEXEC, bug ? Valery Reznic
@ 2010-03-19 21:07 ` Andrew Morton
2010-03-20 0:37 ` David Newall
0 siblings, 1 reply; 10+ messages in thread
From: Andrew Morton @ 2010-03-19 21:07 UTC (permalink / raw)
To: Valery Reznic; +Cc: linux-kernel
On Thu, 11 Mar 2010 02:56:16 -0800 (PST)
Valery Reznic <valery_reznic@yahoo.com> wrote:
> Hi,
>
> I Have following to scripts:
>
> a.sh
> #!/bin/sh
> echo "It's a.sh
>
> and b.sh:
> #! ./b.sh
> echo "It's b.sh"
>
> As per execve man page, script interpreter should not be script itself.
> When I run it on my Fedora 8 x86_64 box (with stock kernel, never updated)
> under strace I got following:
>
> strace -f -e execve setarch x86_64 ./b.sh
> execve("/usr/bin/setarch", ["setarch", "x86_64", "./b.sh"], [/* 23 vars */]) = 0
> execve("./b.sh", ["./b.sh"], [/* 23 vars */]) = -1 ENOEXEC (Exec format error)
> execve("/bin/sh", ["/bin/sh", "./b.sh"], [/* 23 vars */]) = 0
> It's b.sh
>
> I.e execve failed as it should
>
> When I run same scripts on Fedora 12 x86_64 box with stock kernel 2.6.31.5-127.fc12.x86_64 I got following:
>
> strace -f -e execve setarch i386 ./b.sh
> execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"], [/* 41 vars */]) = 0
> execve("./b.sh", ["./b.sh"], [/* 41 vars */]) = 0
> It's a.sh
>
> I.e execve succeeded, instead of failing with ENOEXEC
>
It works for me, I think:
z:/home/akpm> uname -a
Linux z 2.6.31.5-127.fc12.x86_64 #1 SMP Sat Nov 7 21:11:14 EST 2009 x86_64 x86_64 x86_64 GNU/Linux
z:/home/akpm> cat b.sh
#! ./b.sh
echo "It's b.sh"
z:/home/akpm> strace -f -e execve setarch i386 ./b.sh
execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"], [/* 60 vars */]) = 0
execve("./b.sh", ["./b.sh"], [/* 60 vars */]) = -1 ENOEXEC (Exec format error)
execve("/bin/sh", ["/bin/sh", "./b.sh"], [/* 60 vars */]) = 0
It's b.sh
Did I do something wrong? If not, I wonder what's different.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-19 21:07 ` Andrew Morton
@ 2010-03-20 0:37 ` David Newall
2010-03-20 6:42 ` Valery Reznic
0 siblings, 1 reply; 10+ messages in thread
From: David Newall @ 2010-03-20 0:37 UTC (permalink / raw)
To: Valery Reznic; +Cc: linux-kernel
On Thu, 11 Mar 2010 02:56:16 -0800 (PST) Valery Reznic
<valery_reznic@yahoo.com> wrote:
> Hi,
>
> I Have following to scripts:
>
> a.sh
> #!/bin/sh
> echo "It's a.sh
>
> and b.sh:
> #! ./b.sh
> echo "It's b.sh"
>
[...]
> When I run same scripts on Fedora 12 x86_64 box with stock kernel 2.6.31.5-127.fc12.x86_64 I got following:
>
> strace -f -e execve setarch i386 ./b.sh
> execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"], [/* 41 vars */]) = 0
> execve("./b.sh", ["./b.sh"], [/* 41 vars */]) = 0
> It's a.sh
I see no circumstance which would make b.sh invoke a.sh (and thus emit
"It's a.sh"). Are you sure these are the actual scripts and output?
On the other hand, if the output was "It's b.sh", this is compatible
with many historical versions of UNIX, which assumed /bin/sh to be the
script interpreter. On
2.6.28-16-generic #55-Ubuntu SMP i686 GNU/Linux I get successful output
for the following variants of "x.sh":
:
echo worked
and
#!
echo worked
and
#! ./x.sh
echo worked
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-20 0:37 ` David Newall
@ 2010-03-20 6:42 ` Valery Reznic
2010-03-20 9:41 ` David Newall
0 siblings, 1 reply; 10+ messages in thread
From: Valery Reznic @ 2010-03-20 6:42 UTC (permalink / raw)
To: David Newall; +Cc: linux-kernel
--- On Sat, 3/20/10, David Newall <davidn@davidnewall.com> wrote:
> From: David Newall <davidn@davidnewall.com>
> Subject: Re: execve for script don't return ENOEXEC, bug ?
> To: "Valery Reznic" <valery_reznic@yahoo.com>
> Cc: linux-kernel@vger.kernel.org
> Date: Saturday, March 20, 2010, 2:37 AM
> On Thu, 11 Mar 2010 02:56:16 -0800
> (PST) Valery Reznic <valery_reznic@yahoo.com>
> wrote:
> > Hi,
> >
> > I Have following to scripts:
> >
> > a.sh
> > #!/bin/sh
> > echo "It's a.sh
> >
> > and b.sh:
> > #! ./b.sh
> > echo "It's b.sh"
> >
> [...]
> > When I run same scripts on Fedora 12 x86_64 box with
> stock kernel 2.6.31.5-127.fc12.x86_64 I got following:
> >
> > strace -f -e execve setarch i386 ./b.sh
> execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"],
> [/* 41 vars */]) = 0
> > execve("./b.sh", ["./b.sh"], [/* 41 vars */]) = 0
> > It's a.sh
>
> I see no circumstance which would make b.sh invoke a.sh
> (and thus emit "It's a.sh"). Are you sure these are the
> actual scripts and output?
Of course you are right. Somehow I messed up b.sh
(OK, this file is so long and complicated, so no wonder :)
Anyway my bad, sorry.
In the b.sh interpreter should be ./a.sh
Another attempt to provide correct data:
[valery@localhost ~]$ cat a.sh
#!/bin/sh
echo "It's a.sh"
[valery@localhost ~]$ cat b.sh
#! ./a.sh
echo "It's b.sh"
[valery@localhost ~]$
[valery@localhost ~]$ strace -f -e execve setarch i386 ./b.sh
execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"], [/* 40 vars */]) = 0
execve("./b.sh", ["./b.sh"], [/* 40 vars */]) = 0
It's a.sh
[valery@localhost ~]$
>
> On the other hand, if the output was "It's b.sh", this is
> compatible with many historical versions of UNIX, which
> assumed /bin/sh to be the script interpreter. On
> 2.6.28-16-generic #55-Ubuntu SMP i686 GNU/Linux I get
> successful output for the following variants of "x.sh":
>
> :
> echo worked
>
> and
>
> #!
> echo worked
>
> and
>
> #! ./x.sh
> echo worked
My problem is not incorrect output, but successful execve, when script's interpreter is interpreter itself.
Somewhere between Fedora 8 and Fedora 12 execve's behaviour changed.
@Andrew:
When b.sh has interpreter ./b.sh I got expected ENOEXEC, same as you.
Regards,
Valery.
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-20 6:42 ` Valery Reznic
@ 2010-03-20 9:41 ` David Newall
2010-03-20 12:56 ` Valery Reznic
0 siblings, 1 reply; 10+ messages in thread
From: David Newall @ 2010-03-20 9:41 UTC (permalink / raw)
To: Valery Reznic; +Cc: linux-kernel
Valery Reznic wrote:
> [valery@localhost ~]$ cat a.sh
> #!/bin/sh
> echo "It's a.sh"
> [valery@localhost ~]$ cat b.sh
> #! ./a.sh
> echo "It's b.sh"
> [valery@localhost ~]$
> [valery@localhost ~]$ strace -f -e execve setarch i386 ./b.sh
> execve("/usr/bin/setarch", ["setarch", "i386", "./b.sh"], [/* 40 vars */]) = 0
> execve("./b.sh", ["./b.sh"], [/* 40 vars */]) = 0
> It's a.sh
>
That is the correct output for a script which is being interpreted by
a.sh, when a.sh prints "It's a.sh" using /bin/sh as its interpreter.
Remember, you didn't ask /bin/sh to interpret b.sh, you asked a.sh to do
it, and a.sh is a simple echo statement, not an interpreter. There is
no error here.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-20 9:41 ` David Newall
@ 2010-03-20 12:56 ` Valery Reznic
2010-03-20 17:57 ` David Newall
0 siblings, 1 reply; 10+ messages in thread
From: Valery Reznic @ 2010-03-20 12:56 UTC (permalink / raw)
To: David Newall; +Cc: linux-kernel
--- On Sat, 3/20/10, David Newall <davidn@davidnewall.com> wrote:
> From: David Newall <davidn@davidnewall.com>
> Subject: Re: execve for script don't return ENOEXEC, bug ?
> To: "Valery Reznic" <valery_reznic@yahoo.com>
> Cc: linux-kernel@vger.kernel.org
> Date: Saturday, March 20, 2010, 11:41 AM
> Valery Reznic wrote:
> > [valery@localhost ~]$ cat a.sh #!/bin/sh
> > echo "It's a.sh"
> > [valery@localhost ~]$ cat b.sh #! ./a.sh
> > echo "It's b.sh"
> > [valery@localhost ~]$ [valery@localhost ~]$ strace -f
> -e execve setarch i386 ./b.sh execve("/usr/bin/setarch",
> ["setarch", "i386", "./b.sh"], [/* 40 vars */]) = 0
> > execve("./b.sh", ["./b.sh"], [/* 40 vars */]) = 0
> > It's a.sh
> >
>
> That is the correct output for a script which is being
> interpreted by a.sh, when a.sh prints "It's a.sh" using
> /bin/sh as its interpreter. Remember, you didn't ask
> /bin/sh to interpret b.sh, you asked a.sh to do it, and a.sh
> is a simple echo statement, not an interpreter. There
> is no error here.
execve's man page state that script's interprtert should not be
interpreter itself:
------------------------------------------------------
Interpreter scripts
An interpreter script is a text file that has execute permission
enabled and whose first line is of the form:
#! interpreter [optional-arg]
The interpreter must be a valid pathname for an executable which is not
itself a script.
------------------------------------------------------
I.e, execve should return ENOEXEC. And it did it at least in Fedora 8 and earlier.
To me it looks like execve and it's man page disagree. Do you know is it new intended behaviour of execve and just man page wasn't update or it's a bug in execve ?
Valery.
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-20 12:56 ` Valery Reznic
@ 2010-03-20 17:57 ` David Newall
2010-03-21 8:33 ` Valery Reznic
0 siblings, 1 reply; 10+ messages in thread
From: David Newall @ 2010-03-20 17:57 UTC (permalink / raw)
To: Valery Reznic; +Cc: linux-kernel
Valery Reznic wrote:
> execve's man page state that script's interprtert should not be
> interpreter itself:
> ------------------------------------------------------
> Interpreter scripts
> An interpreter script is a text file that has execute permission
> enabled and whose first line is of the form:
>
> #! interpreter [optional-arg]
>
> The interpreter must be a valid pathname for an executable which is not
> itself a script.
> ------------------------------------------------------
>
> I.e, execve should return ENOEXEC. And it did it at least in Fedora 8 and earlier.
>
> To me it looks like execve and it's man page disagree. Do you know is it new intended behaviour of execve and just man page wasn't update or it's a bug in execve ?
Code and man pages do sometimes disagree. I shan't address what the
correct behaviour is, because if you ask three people you're sure to get
four different answers, rather let's discuss what is desirable. Without
looking at how it works, we observe that a.sh can be executed without
error. If a.out were written in C it would qualify as an acceptable
interpreter according to the man page, so why should it not qualify if
it is interpreted? I think it's desirable that it does qualify. There
could be sound reasons why only one level of interpreter can be
invoked. Perhaps loading a script interpreter is done as an exception
in exec, and it's too ugly to allow recursive exceptions. That would be
a fair reason. But if there's no reason, then don't have the
restriction*. Linux now apparently does permit interpreted
interpreters, and I say that is the desirable result.
*Newall's second rule of programming: A program should impose no
unnecessary restriction on its user.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
2010-03-20 17:57 ` David Newall
@ 2010-03-21 8:33 ` Valery Reznic
2010-03-21 19:16 ` Johannes Stezenbach
0 siblings, 1 reply; 10+ messages in thread
From: Valery Reznic @ 2010-03-21 8:33 UTC (permalink / raw)
To: David Newall; +Cc: linux-kernel
--- On Sat, 3/20/10, David Newall <davidn@davidnewall.com> wrote:
> From: David Newall <davidn@davidnewall.com>
> Subject: Re: execve for script don't return ENOEXEC, bug ?
> To: "Valery Reznic" <valery_reznic@yahoo.com>
> Cc: linux-kernel@vger.kernel.org
> Date: Saturday, March 20, 2010, 7:57 PM
> Valery Reznic wrote:
> > execve's man page state that script's interprtert
> should not be interpreter itself:
> >
> ------------------------------------------------------
> > Interpreter scripts
> > An interpreter
> script is a text file that has
> execute permission
> > enabled and whose first
> line is of the form:
> >
> > #!
> interpreter [optional-arg]
> >
> > The interpreter must be a
> valid pathname for an executable which is not
> > itself a
> script.
> ------------------------------------------------------
> >
> > I.e, execve should return ENOEXEC. And it did it at
> least in Fedora 8 and earlier.
> >
> > To me it looks like execve and it's man page
> disagree. Do you know is it new intended behaviour of execve
> and just man page wasn't update or it's a bug in execve ?
>
> Code and man pages do sometimes disagree. I shan't
> address what the correct behaviour is, because if you ask
> three people you're sure to get four different answers,
> rather let's discuss what is desirable. Without
> looking at how it works, we observe that a.sh can be
> executed without error. If a.out were written in C it
> would qualify as an acceptable interpreter according to the
> man page, so why should it not qualify if it is
> interpreted? I think it's desirable that it does
> qualify. There could be sound reasons why only one
> level of interpreter can be invoked. Perhaps loading a
> script interpreter is done as an exception in exec, and it's
> too ugly to allow recursive exceptions. That would be
> a fair reason. But if there's no reason, then don't
> have the restriction*. Linux now apparently does
> permit interpreted interpreters, and I say that is the
> desirable result.
For some reason I tough that ENOEXEC for 'interpreted interpreter' is posix requirement. But after closer look it appear to be only arbitrary restriction now lifted in Linux.
I had a look at the source http://tomoyo.sourceforge.jp/cgi-bin/lxr/source/fs/binfmt_misc.c
and it's obvious that 'interpreted interpreter' is intentional (and recursion depth is 4).
So, execve is behave as it should and only man page is lag behind.
Thank you for you help/
Just curios - who use this feature in the real world and what for ?
Valery.
>
> *Newall's second rule of programming: A program should
> impose no unnecessary restriction on its user.
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
@ 2010-03-21 19:16 ` Johannes Stezenbach
0 siblings, 0 replies; 10+ messages in thread
From: Johannes Stezenbach @ 2010-03-21 19:16 UTC (permalink / raw)
To: Valery Reznic; +Cc: David Newall, linux-kernel, Michael Kerrisk, linux-man
(Cc: man page maintainer)
On Sun, Mar 21, 2010 at 01:33:28AM -0700, Valery Reznic wrote:
> --- On Sat, 3/20/10, David Newall <davidn@davidnewall.com> wrote:
> > Valery Reznic wrote:
> > > execve's man page state that script's interprtert
> > > should not be interpreter itself:
...
> > > To me it looks like execve and it's man page
> > > disagree. Do you know is it new intended behaviour of execve
> > > and just man page wasn't update or it's a bug in execve ?
> >
> > Code and man pages do sometimes disagree. I shan't
> > address what the correct behaviour is, because if you ask
> > three people you're sure to get four different answers,
> > rather let's discuss what is desirable. Without
> > looking at how it works, we observe that a.sh can be
> > executed without error. If a.out were written in C it
> > would qualify as an acceptable interpreter according to the
> > man page, so why should it not qualify if it is
> > interpreted? I think it's desirable that it does
> > qualify. There could be sound reasons why only one
> > level of interpreter can be invoked. Perhaps loading a
> > script interpreter is done as an exception in exec, and it's
> > too ugly to allow recursive exceptions. That would be
> > a fair reason. But if there's no reason, then don't
> > have the restriction*. Linux now apparently does
> > permit interpreted interpreters, and I say that is the
> > desirable result.
> For some reason I tough that ENOEXEC for 'interpreted interpreter' is posix
> requirement. But after closer look it appear to be only arbitrary restriction
> now lifted in Linux.
>
> I had a look at the source http://tomoyo.sourceforge.jp/cgi-bin/lxr/source/fs/binfmt_misc.c
> and it's obvious that 'interpreted interpreter' is intentional (and recursion depth is 4).
> So, execve is behave as it should and only man page is lag behind.
> Thank you for you help/
>
>
> Just curios - who use this feature in the real world and what for ?
It seems to have been changed in commit bf2a9a39639b8b51377905397a5005f444e9a892.
Maybe you could ask the author for details.
Johannes
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: execve for script don't return ENOEXEC, bug ?
@ 2010-03-21 19:16 ` Johannes Stezenbach
0 siblings, 0 replies; 10+ messages in thread
From: Johannes Stezenbach @ 2010-03-21 19:16 UTC (permalink / raw)
To: Valery Reznic
Cc: David Newall, linux-kernel-u79uwXL29TY76Z2rM5mHXA,
Michael Kerrisk, linux-man-u79uwXL29TY76Z2rM5mHXA
(Cc: man page maintainer)
On Sun, Mar 21, 2010 at 01:33:28AM -0700, Valery Reznic wrote:
> --- On Sat, 3/20/10, David Newall <davidn-KzQzY1MbaKjAHznzqCTclw@public.gmane.org> wrote:
> > Valery Reznic wrote:
> > > execve's man page state that script's interprtert
> > > should not be interpreter itself:
...
> > > To me it looks like execve and it's man page
> > > disagree. Do you know is it new intended behaviour of execve
> > > and just man page wasn't update or it's a bug in execve ?
> >
> > Code and man pages do sometimes disagree. I shan't
> > address what the correct behaviour is, because if you ask
> > three people you're sure to get four different answers,
> > rather let's discuss what is desirable. Without
> > looking at how it works, we observe that a.sh can be
> > executed without error. If a.out were written in C it
> > would qualify as an acceptable interpreter according to the
> > man page, so why should it not qualify if it is
> > interpreted? I think it's desirable that it does
> > qualify. There could be sound reasons why only one
> > level of interpreter can be invoked. Perhaps loading a
> > script interpreter is done as an exception in exec, and it's
> > too ugly to allow recursive exceptions. That would be
> > a fair reason. But if there's no reason, then don't
> > have the restriction*. Linux now apparently does
> > permit interpreted interpreters, and I say that is the
> > desirable result.
> For some reason I tough that ENOEXEC for 'interpreted interpreter' is posix
> requirement. But after closer look it appear to be only arbitrary restriction
> now lifted in Linux.
>
> I had a look at the source http://tomoyo.sourceforge.jp/cgi-bin/lxr/source/fs/binfmt_misc.c
> and it's obvious that 'interpreted interpreter' is intentional (and recursion depth is 4).
> So, execve is behave as it should and only man page is lag behind.
> Thank you for you help/
>
>
> Just curios - who use this feature in the real world and what for ?
It seems to have been changed in commit bf2a9a39639b8b51377905397a5005f444e9a892.
Maybe you could ask the author for details.
Johannes
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^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2010-03-21 19:16 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-03-11 10:56 execve for script don't return ENOEXEC, bug ? Valery Reznic
2010-03-19 21:07 ` Andrew Morton
2010-03-20 0:37 ` David Newall
2010-03-20 6:42 ` Valery Reznic
2010-03-20 9:41 ` David Newall
2010-03-20 12:56 ` Valery Reznic
2010-03-20 17:57 ` David Newall
2010-03-21 8:33 ` Valery Reznic
2010-03-21 19:16 ` Johannes Stezenbach
2010-03-21 19:16 ` Johannes Stezenbach
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