From: Wander Lairson Costa <wander@redhat.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
Eric Biederman <ebiederm@xmission.com>,
Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Laurent Vivier <laurent@vivier.eu>,
Wander Lairson Costa <wander@redhat.com>,
YunQiang Su <ysu@wavecomp.com>, Helge Deller <deller@gmx.de>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>, Alexey Gladkov <legion@kernel.org>,
David Hildenbrand <david@redhat.com>,
Rolf Eike Beer <eb@emlix.com>,
linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS and
infrastructure)), linux-kernel@vger.kernel.org (open list)
Subject: [PATCH RFC v2 0/4] coredump: mitigate privilege escalation of process coredump
Date: Tue, 28 Dec 2021 14:09:04 -0300 [thread overview]
Message-ID: <20211228170910.623156-1-wander@redhat.com> (raw)
v2
==
Patch 02 conflicted with commit 92307383082d("coredump: Don't perform
any cleanups before dumping core") which I didn't have in my tree. V2
just changes the hunk
+#define PF_SUID 0x00000008
To
+#define PF_SUID 0x01000000
To merge cleanly. Other than that, it is the same patch as v1.
v1
==
A set-uid executable might be a vector to privilege escalation if the
system configures the coredump file name pattern as a relative
directory destiny. The full description of the vulnerability and
a demonstration of how we can exploit it can be found at [1].
This patch series adds a PF_SUID flag to the process in execve if it is
set-[ug]id binary and elevates the new image's privileges.
In the do_coredump function, we check if:
1) We have the SUID_FLAG set
2) We have CAP_SYS_ADMIN (the process might have decreased its
privileges)
3) The current directory is owned by root (the current code already
checks for core_pattern being a relative path).
4) non-privileged users don't have permission to write to the current
directory.
If all four conditions match, we set the need_suid_safe flag.
An alternative implementation (and more elegant IMO) would be saving
the fsuid and fsgid of the process in the task_struct before loading the
new image to the memory. But this approach would add eight bytes to all
task_struct instances where only a tiny fraction of the processes need
it and under a configuration that not all (most?) distributions don't
adopt by default.
Wander Lairson Costa (4):
exec: add a flag indicating if an exec file is a suid/sgid
process: add the PF_SUID flag
coredump: mitigate privilege escalation of process coredump
exec: only set the suid flag if the current proc isn't root
fs/coredump.c | 15 +++++++++++++++
fs/exec.c | 10 ++++++++++
include/linux/binfmts.h | 6 +++++-
include/linux/sched.h | 1 +
kernel/fork.c | 2 ++
5 files changed, 33 insertions(+), 1 deletion(-)
--
2.27.0
next reply other threads:[~2021-12-28 17:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-28 17:09 Wander Lairson Costa [this message]
2021-12-28 17:09 ` [PATCH RFC v2 1/4] exec: add a flag indicating if an exec file is a suid/sgid Wander Lairson Costa
2021-12-28 17:09 ` [PATCH RFC v2 2/4] process: add the PF_SUID flag Wander Lairson Costa
2021-12-28 17:09 ` [PATCH RFC v2 3/4] coredump: mitigate privilege escalation of process coredump Wander Lairson Costa
2021-12-28 17:09 ` [PATCH RFC v2 4/4] exec: only set the suid flag if the current proc isn't root Wander Lairson Costa
2022-01-03 22:11 ` [PATCH RFC v2 0/4] coredump: mitigate privilege escalation of process coredump Eric W. Biederman
2022-01-05 12:30 ` Wander Costa
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=20211228170910.623156-1-wander@redhat.com \
--to=wander@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=axboe@kernel.dk \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=david@redhat.com \
--cc=deller@gmx.de \
--cc=dietmar.eggemann@arm.com \
--cc=eb@emlix.com \
--cc=ebiederm@xmission.com \
--cc=juri.lelli@redhat.com \
--cc=keescook@chromium.org \
--cc=laurent@vivier.eu \
--cc=legion@kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=vincent.guittot@linaro.org \
--cc=viro@zeniv.linux.org.uk \
--cc=ysu@wavecomp.com \
/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: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).