GNU bug report logs - #52800
[PATCH] maint: fix prctl arguments

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Pádraig Brady <P <at> draigBrady.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#52800: closed ([PATCH] maint: fix prctl arguments)
Date: Sun, 26 Dec 2021 17:27:01 +0000

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Your message dated Sun, 26 Dec 2021 17:26:20 +0000
with message-id <f6c11b37-3fc2-1d9f-f912-3268eb2a3861 <at> draigBrady.com>
and subject line Re: bug#52800: [PATCH] maint: fix prctl arguments
has caused the debbugs.gnu.org bug report #52800,
regarding [PATCH] maint: fix prctl arguments
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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From: Max Filippov <jcmvbkbc <at> gmail.com>
To: bug-coreutils <at> gnu.org
Cc: Max Filippov <jcmvbkbc <at> gmail.com>
Subject: [PATCH] maint: fix prctl arguments
Date: Sat, 25 Dec 2021 21:17:44 -0800

When configured with --enable-single-binary tools issue incorrect prctl:

  prctl(PR_SET_KEEPCAPS, 1071091381)      = -1 EINVAL (Invalid argument)

PR_SET_MM_ARG_START is not a prctl 'option' parameter, it's 'arg2'
parameter for the option PR_SET_MM. It also has to have 'arg4' and
'arg5' set to 0 explicitly, otherwise the kernel also returns -EINVAL.

* src/coreutils.c (launch_program): Fix prctl arguments.
---
 src/coreutils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/coreutils.c b/src/coreutils.c
index 6db5a8f05ce3..d8f6e97a6d2f 100644
--- a/src/coreutils.c
+++ b/src/coreutils.c
@@ -121,7 +121,7 @@ launch_program (char const *prog_name, int prog_argc, char **prog_argv)
 #if HAVE_PRCTL && defined PR_SET_MM_ARG_START
   /* Shift the beginning of the command line to prog_argv[0] (if set) so
      /proc/pid/cmdline reflects the right value.  */
-  prctl (PR_SET_MM_ARG_START, prog_argv[0]);
+  prctl (PR_SET_MM, PR_SET_MM_ARG_START, prog_argv[0], 0, 0);
 #endif
 
   exit (prog_main (prog_argc, prog_argv));
-- 
2.20.1

[Message part 3 (message/rfc822, inline)]

From: Pádraig Brady <P <at> draigBrady.com>
To: Max Filippov <jcmvbkbc <at> gmail.com>, 52800-done <at> debbugs.gnu.org
Subject: Re: bug#52800: [PATCH] maint: fix prctl arguments
Date: Sun, 26 Dec 2021 17:26:20 +0000

On 26/12/2021 05:17, Max Filippov wrote:
> When configured with --enable-single-binary tools issue incorrect prctl:
> 
>    prctl(PR_SET_KEEPCAPS, 1071091381)      = -1 EINVAL (Invalid argument)
> 
> PR_SET_MM_ARG_START is not a prctl 'option' parameter, it's 'arg2'
> parameter for the option PR_SET_MM. It also has to have 'arg4' and
> 'arg5' set to 0 explicitly, otherwise the kernel also returns -EINVAL.
> 
> * src/coreutils.c (launch_program): Fix prctl arguments.
> ---
>   src/coreutils.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/coreutils.c b/src/coreutils.c
> index 6db5a8f05ce3..d8f6e97a6d2f 100644
> --- a/src/coreutils.c
> +++ b/src/coreutils.c
> @@ -121,7 +121,7 @@ launch_program (char const *prog_name, int prog_argc, char **prog_argv)
>   #if HAVE_PRCTL && defined PR_SET_MM_ARG_START
>     /* Shift the beginning of the command line to prog_argv[0] (if set) so
>        /proc/pid/cmdline reflects the right value.  */
> -  prctl (PR_SET_MM_ARG_START, prog_argv[0]);
> +  prctl (PR_SET_MM, PR_SET_MM_ARG_START, prog_argv[0], 0, 0);
>   #endif
>   
>     exit (prog_main (prog_argc, prog_argv));

Nice one.

This functionality allows programs like ps to attribute
to more specific "utilities", rather than the general "coreutils" binary.

However this is only available with CAP_SYS_RESOURCE or root.
Note CAP_SYS_RESOURCE wouldn't be appropriate to set on the coreutils binary in general.
I confirmed your patch is effective for coreutils invoked by root with:

$ src/sleep 5 & { sleep 1; tr '\0' '\n' < /proc/$!/cmdline; }
/home/padraig/git/coreutils/src/coreutils
--coreutils-prog-shebang=sleep
src/sleep
5

# src/sleep 5 & { sleep 1; tr '\0' '\n' < /proc/$!/cmdline; }
sleep
5

I'll apply later (with some adjustments to NEWS)
Marking this as done.

thanks!
Pádraig

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