From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) To: Nicolas Iooss <nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Alexander Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: [PATCH 1/2] coredump: use from_kuid/kgid_munged when formatting corename Date: Tue, 05 May 2015 14:13:24 -0500 [thread overview] Message-ID: <87bnhyhm7f.fsf@x220.int.ebiederm.org> (raw) In-Reply-To: <1430649246-32726-1-git-send-email-nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> (Nicolas Iooss's message of "Sun, 3 May 2015 18:34:05 +0800") Nicolas Iooss <nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> writes: > When adding __printf attribute to cn_printf, gcc reports some issues: > > fs/coredump.c:213:5: warning: format '%d' expects argument of type > 'int', but argument 3 has type 'kuid_t' [-Wformat=] > err = cn_printf(cn, "%d", cred->uid); > ^ > fs/coredump.c:217:5: warning: format '%d' expects argument of type > 'int', but argument 3 has type 'kgid_t' [-Wformat=] > err = cn_printf(cn, "%d", cred->gid); > ^ > > These warnings come from the fact that the value of uid/gid needs to be > extracted from the kuid_t/kgid_t structure before being used as an > integer. More precisely, cred->uid and cred->gid need to be converted > to either user-namespace uid/gid or to init_user_ns uid/gid. > > As Documentation/sysctl/kernel.txt does not specify which user namespace > is used to translate %u and %g in core_pattern, but lowercase %p and %i > are used to format pid/tid in the current process namespace, it seems > intuitive that lowercase %u and %g use the current user namespace. I love the logic of lower vs upper case letters in the selection of how an identifier should be used. Unfortunately I can't support it. Converting to anything other than init_user_ns will actually be an ABI break. Which in practice should trump everything else. Further only the global root user can set this value, which largely implies that the program setting the core dump patter will expect the values to be in the initial user namespace. In practice your patch allows any user to put any uid they want on core files which seems to make the uid parameter useless. So for all of the reasons above I think we need to print uids and gids in the initial user namespace unless explicitly requested to do so. > While at it, format uid and gid values with %u instead of %d because > uid_t/__kernel_uid32_t and gid_t/__kernel_gid32_t are unsigned int. > > Signed-off-by: Nicolas Iooss <nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> > --- > fs/coredump.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/coredump.c b/fs/coredump.c > index bbbe139ab280..99c8af640c5a 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -209,11 +209,15 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm) > break; > /* uid */ > case 'u': > - err = cn_printf(cn, "%d", cred->uid); > + err = cn_printf(cn, "%u", > + from_kuid_munged(cred->user_ns, > + cred->uid)); > break; > /* gid */ > case 'g': > - err = cn_printf(cn, "%d", cred->gid); > + err = cn_printf(cn, "%u", > + from_kgid_munged(cred->user_ns, > + cred->gid)); > break; > case 'd': > err = cn_printf(cn, "%d",
WARNING: multiple messages have this Message-ID (diff)
From: ebiederm@xmission.com (Eric W. Biederman) To: Nicolas Iooss <nicolas.iooss_linux@m4x.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, Linux Containers <containers@lists.linux-foundation.org> Subject: Re: [PATCH 1/2] coredump: use from_kuid/kgid_munged when formatting corename Date: Tue, 05 May 2015 14:13:24 -0500 [thread overview] Message-ID: <87bnhyhm7f.fsf@x220.int.ebiederm.org> (raw) In-Reply-To: <1430649246-32726-1-git-send-email-nicolas.iooss_linux@m4x.org> (Nicolas Iooss's message of "Sun, 3 May 2015 18:34:05 +0800") Nicolas Iooss <nicolas.iooss_linux@m4x.org> writes: > When adding __printf attribute to cn_printf, gcc reports some issues: > > fs/coredump.c:213:5: warning: format '%d' expects argument of type > 'int', but argument 3 has type 'kuid_t' [-Wformat=] > err = cn_printf(cn, "%d", cred->uid); > ^ > fs/coredump.c:217:5: warning: format '%d' expects argument of type > 'int', but argument 3 has type 'kgid_t' [-Wformat=] > err = cn_printf(cn, "%d", cred->gid); > ^ > > These warnings come from the fact that the value of uid/gid needs to be > extracted from the kuid_t/kgid_t structure before being used as an > integer. More precisely, cred->uid and cred->gid need to be converted > to either user-namespace uid/gid or to init_user_ns uid/gid. > > As Documentation/sysctl/kernel.txt does not specify which user namespace > is used to translate %u and %g in core_pattern, but lowercase %p and %i > are used to format pid/tid in the current process namespace, it seems > intuitive that lowercase %u and %g use the current user namespace. I love the logic of lower vs upper case letters in the selection of how an identifier should be used. Unfortunately I can't support it. Converting to anything other than init_user_ns will actually be an ABI break. Which in practice should trump everything else. Further only the global root user can set this value, which largely implies that the program setting the core dump patter will expect the values to be in the initial user namespace. In practice your patch allows any user to put any uid they want on core files which seems to make the uid parameter useless. So for all of the reasons above I think we need to print uids and gids in the initial user namespace unless explicitly requested to do so. > While at it, format uid and gid values with %u instead of %d because > uid_t/__kernel_uid32_t and gid_t/__kernel_gid32_t are unsigned int. > > Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org> > --- > fs/coredump.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/coredump.c b/fs/coredump.c > index bbbe139ab280..99c8af640c5a 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -209,11 +209,15 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm) > break; > /* uid */ > case 'u': > - err = cn_printf(cn, "%d", cred->uid); > + err = cn_printf(cn, "%u", > + from_kuid_munged(cred->user_ns, > + cred->uid)); > break; > /* gid */ > case 'g': > - err = cn_printf(cn, "%d", cred->gid); > + err = cn_printf(cn, "%u", > + from_kgid_munged(cred->user_ns, > + cred->gid)); > break; > case 'd': > err = cn_printf(cn, "%d",
next prev parent reply other threads:[~2015-05-05 19:13 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-04-16 10:28 [PATCH RESENT] coredump: fix cn_printf formatting warnings Nicolas Iooss 2015-04-16 10:50 ` Joe Perches 2015-05-03 10:34 ` [PATCH 1/2] coredump: use from_kuid/kgid_munged when formatting corename Nicolas Iooss 2015-05-03 10:34 ` [PATCH 2/2] coredump: add __printf attribute to cn_*printf functions Nicolas Iooss [not found] ` <1430649246-32726-1-git-send-email-nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> 2015-05-05 19:13 ` Eric W. Biederman [this message] 2015-05-05 19:13 ` [PATCH 1/2] coredump: use from_kuid/kgid_munged when formatting corename Eric W. Biederman [not found] ` <87bnhyhm7f.fsf-JOvCrm2gF+uungPnsOpG7nhyD016LWXt@public.gmane.org> 2015-05-06 12:18 ` Nicolas Iooss 2015-05-06 12:18 ` Nicolas Iooss [not found] ` <554A0684.2000400-oWGTIYur0i8@public.gmane.org> 2015-05-15 2:29 ` [PATCH v2 1/2] coredump: use from_kuid/kgid " Nicolas Iooss 2015-05-15 2:29 ` Nicolas Iooss 2015-05-15 2:29 ` [PATCH v2 2/2] coredump: add __printf attribute to cn_*printf functions Nicolas Iooss [not found] ` <1431656975-3563-2-git-send-email-nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> 2015-05-15 14:54 ` Eric W. Biederman 2015-05-15 14:54 ` Eric W. Biederman [not found] ` <1431656975-3563-1-git-send-email-nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org> 2015-05-15 2:29 ` Nicolas Iooss 2015-05-15 14:52 ` [PATCH v2 1/2] coredump: use from_kuid/kgid when formatting corename Eric W. Biederman 2015-05-15 14:52 ` Eric W. Biederman
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=87bnhyhm7f.fsf@x220.int.ebiederm.org \ --to=ebiederm-as9lmozglivwk0htik3j/w@public.gmane.org \ --cc=akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org \ --cc=containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org \ --cc=linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \ --cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \ --cc=nicolas.iooss_linux-oWGTIYur0i8@public.gmane.org \ --cc=viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.