From: Matt Bobrowski <mattbobrowski@google.com>
To: kpsingh@kernel.org, ast@kernel.org, andrii@kernel.org
Cc: revest@chromium.org, jackmanb@chromium.org,
yonghong.song@linux.dev, gnoack@google.com, bpf@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH bpf-next] bpf: add security_file_mprotect() to sleepable_lsm_hooks BTF set
Date: Thu, 1 Feb 2024 13:38:20 +0000 [thread overview]
Message-ID: <ZbuezASA0_Ng2VB9@google.com> (raw)
In-Reply-To: <Zbt16HS-9x8YPZNz@google.com>
On Thu, Feb 01, 2024 at 10:43:52AM +0000, Matt Bobrowski wrote:
> security_file_mprotect() is missing from the sleepable_lsm_hooks BTF
> set. Add it so that operations performed by a BPF program which may
> result in the thread being put to sleep are permitted.
>
> Building a kernel with the DEBUG_ATOMIC_SLEEP confiuration option
> enabled and running reasonable workloads stimulating a BPF program
> attached to security_file_mprotect() which could end up performing an
> operation that could sleep resulted in no splats.
Actually, no, please disregard this patch. It was only a matter of
timing before something had popped up.
This was sent out far too prematurely and I failed to realize that
__bpf_prog_enter_sleepable() calls might_fault() and
security_file_mprotect() is being called from a context whereby a
mmap_lock is already being held. In essence, this also means that it's
not possible to run sleepable BPF programs in contexts where a
mmap_lock is already held as the page fault handler also attempts to
take the mmap_lock, and well all know what happens when you have the
same thread attempting to acquire the same lock whilst already holding
that lock.
> Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
> ---
> kernel/bpf/bpf_lsm.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> index 68240c3c6e7d..da52c955f3ca 100644
> --- a/kernel/bpf/bpf_lsm.c
> +++ b/kernel/bpf/bpf_lsm.c
> @@ -277,10 +277,13 @@ BTF_ID(func, bpf_lsm_bprm_creds_from_file)
> BTF_ID(func, bpf_lsm_capget)
> BTF_ID(func, bpf_lsm_capset)
> BTF_ID(func, bpf_lsm_cred_prepare)
> +
> BTF_ID(func, bpf_lsm_file_ioctl)
> BTF_ID(func, bpf_lsm_file_lock)
> BTF_ID(func, bpf_lsm_file_open)
> BTF_ID(func, bpf_lsm_file_receive)
> +BTF_ID(func, bpf_lsm_mmap_file)
> +BTF_ID(func, bpf_lsm_file_mprotect)
>
> BTF_ID(func, bpf_lsm_inode_create)
> BTF_ID(func, bpf_lsm_inode_free_security)
> @@ -316,7 +319,6 @@ BTF_ID(func, bpf_lsm_path_chown)
> BTF_ID(func, bpf_lsm_key_free)
> #endif /* CONFIG_KEYS */
>
> -BTF_ID(func, bpf_lsm_mmap_file)
> BTF_ID(func, bpf_lsm_netlink_send)
> BTF_ID(func, bpf_lsm_path_notify)
> BTF_ID(func, bpf_lsm_release_secctx)
> --
> 2.43.0.429.g432eaa2c6b-goog
/M
prev parent reply other threads:[~2024-02-01 13:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-01 10:43 [PATCH bpf-next] bpf: add security_file_mprotect() to sleepable_lsm_hooks BTF set Matt Bobrowski
2024-02-01 13:38 ` Matt Bobrowski [this message]
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=ZbuezASA0_Ng2VB9@google.com \
--to=mattbobrowski@google.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=gnoack@google.com \
--cc=jackmanb@chromium.org \
--cc=kpsingh@kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=revest@chromium.org \
--cc=yonghong.song@linux.dev \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).