From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
To: Paul Moore <paul@paul-moore.com>
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Subject: Re: [PATCH 28/32] selinux: Use mem_to_flex_dup() with xfrm and sidtab
Date: Thu, 5 May 2022 20:08:22 -0500 [thread overview]
Message-ID: <20220506010822.GA18891@embeddedor> (raw)
In-Reply-To: <CAHC9VhT3EDCZEP1og3H_PGFETE6403HUHw7aQb_wDMwJnWeb3Q@mail.gmail.com>
On Thu, May 05, 2022 at 07:16:18PM -0400, Paul Moore wrote:
> On Thu, May 5, 2022 at 2:39 PM Kees Cook <keescook@chromium.org> wrote:
> > On Wed, May 04, 2022 at 11:14:42PM -0400, Paul Moore wrote:
> > > On Wed, May 4, 2022 at 7:34 PM Gustavo A. R. Silva
> > > <gustavoars@kernel.org> wrote:
> > > >
> > > > Hi Paul,
> > > >
> > > > On Wed, May 04, 2022 at 06:57:28PM -0400, Paul Moore wrote:
> > > > > On Tue, May 3, 2022 at 9:57 PM Kees Cook <keescook@chromium.org> wrote:
> > > >
> > > > [..]
> > > >
> > > > > > +++ b/include/uapi/linux/xfrm.h
> > > > > > @@ -31,9 +31,9 @@ struct xfrm_id {
> > > > > > struct xfrm_sec_ctx {
> > > > > > __u8 ctx_doi;
> > > > > > __u8 ctx_alg;
> > > > > > - __u16 ctx_len;
> > > > > > + __DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(__u16, ctx_len);
> > > > > > __u32 ctx_sid;
> > > > > > - char ctx_str[0];
> > > > > > + __DECLARE_FLEX_ARRAY_ELEMENTS(char, ctx_str);
> > > > > > };
> > > > >
> > > > > While I like the idea of this in principle, I'd like to hear about the
> > > > > testing you've done on these patches. A previous flex array
> > > > > conversion in the audit uapi headers ended up causing a problem with
> > > >
> > > > I'm curious about which commit caused those problems...?
> > >
> > > Commit ed98ea2128b6 ("audit: replace zero-length array with
> > > flexible-array member"), however, as I said earlier, the problem was
> > > actually with SWIG, it just happened to be triggered by the kernel
> > > commit. There was a brief fedora-devel mail thread about the problem,
> > > see the link below:
> > >
> > > * https://www.spinics.net/lists/fedora-devel/msg297991.html
> >
> > Wow, that's pretty weird -- it looks like SWIG was scraping the headers
> > to build its conversions? I assume SWIG has been fixed now?
>
> I honestly don't know, the audit userspace was hacking around it with
> some header file duplication/munging last I heard, but I try to avoid
> having to touch Steve's audit userspace code.
>
> > > To reiterate, I'm supportive of changes like this, but I would like to
> > > hear how it was tested to ensure there are no unexpected problems with
> > > userspace. If there are userspace problems it doesn't mean we can't
> > > make changes like this, it just means we need to ensure that the
> > > userspace issues are resolved first.
> >
> > Well, as this is the first and only report of any problems with [0] -> []
> > conversions (in UAPI or anywhere) that I remember seeing, and they've
> > been underway since at least v5.9, I hadn't been doing any new testing.
>
> ... and for whatever it is worth, I wasn't expecting it to be a
> problem either. Surprise :)
>
> > So, for this case, I guess I should ask what tests you think would be
> > meaningful here? Anything using #include should be fine:
> > https://codesearch.debian.net/search?q=linux%2Fxfrm.h&literal=1&perpkg=1
> > Which leaves just this, which may be doing something weird:
> >
> > libabigail_2.0-1/tests/data/test-diff-filter/test-PR27569-v0.abi
> > </data-member>
> > <data-member access="public" layout-offset-in-bits="128">
> > <var-decl name="seq_hi" type-id="3f1a6b60" visibility="default" filepath="include/uapi/linux/xfrm.h" line="97" column="1"/>
> > </data-member>
> > <data-member access="public" layout-offset-in-bits="160">
> >
> > But I see that SWIG doesn't show up in a search for linux/audit.h:
> > https://codesearch.debian.net/search?q=linux%2Faudit.h&literal=1&perpkg=1
> >
> > So this may not be a sufficient analysis...
>
> I think from a practical perspective ensuring that the major IPsec/IKE
> tools, e.g. the various *SWANs, that know about labeled IPSec still
> build and can set/get the SA/SPD labels correctly would be sufficient.
> I seriously doubt there would be any problems, but who knows.
There are certainly some cases in which the transformation of
zero-length arrays into flexible-array members can bring some issues
to the surface[1][2]. This is the first time that we know of one of
them in user-space. However, we haven't transformed the arrays in
UAPI yet (with the exception of a couple of cases[3][4]). But that
is something that we are planning to try soon[5].
--
Gustavo
[1] https://github.com/KSPP/linux/issues?q=invalid+use+of+flexible+array
[2] https://github.com/KSPP/linux/issues?q=invalid+application+of+%E2%80%98sizeof%E2%80%99+to+incomplete+type
[3] https://git.kernel.org/linus/db243b796439c0caba47865564d8acd18a301d18
[4] https://git.kernel.org/linus/d6cdad870358128c1e753e6258e295ab8a5a2429
[5] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?h=for-next/kspp-fam0-uapi
next prev parent reply other threads:[~2022-05-06 0:59 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-04 1:44 [PATCH 00/32] Introduce flexible array struct memcpy() helpers Kees Cook
2022-05-04 1:44 ` [PATCH 01/32] netlink: Avoid memcpy() across flexible array boundary Kees Cook
2022-05-04 3:31 ` Gustavo A. R. Silva
2022-05-04 3:37 ` Kees Cook
2022-05-04 1:44 ` [PATCH 02/32] Introduce flexible array struct memcpy() helpers Kees Cook
2022-05-04 7:25 ` Johannes Berg
2022-05-04 15:38 ` Kees Cook
2022-05-04 16:08 ` David Laight
2022-05-05 13:16 ` Johannes Berg
2022-05-05 15:16 ` Keith Packard
2022-05-05 19:32 ` Kees Cook
2022-05-05 20:08 ` Keith Packard
2022-05-05 20:12 ` Johannes Berg
2022-05-06 11:15 ` David Laight
2022-05-05 19:27 ` Kees Cook
2022-05-04 1:44 ` [PATCH 03/32] flex_array: Add Kunit tests Kees Cook
2022-05-04 3:00 ` David Gow
2022-05-04 19:43 ` Kees Cook
2022-05-04 19:58 ` Daniel Latypov
2022-05-04 1:44 ` [PATCH 04/32] fortify: Add run-time WARN for cross-field memcpy() Kees Cook
2022-05-04 1:44 ` [PATCH 05/32] brcmfmac: Use mem_to_flex_dup() with struct brcmf_fweh_queue_item Kees Cook
2022-05-04 1:44 ` [PATCH 06/32] iwlwifi: calib: Prepare to use mem_to_flex_dup() Kees Cook
2022-05-04 1:44 ` [PATCH 07/32] iwlwifi: calib: Use mem_to_flex_dup() with struct iwl_calib_result Kees Cook
2022-05-04 1:44 ` [PATCH 08/32] iwlwifi: mvm: Use mem_to_flex_dup() with struct ieee80211_key_conf Kees Cook
2022-05-04 1:44 ` [PATCH 09/32] p54: Use mem_to_flex_dup() with struct p54_cal_database Kees Cook
2022-05-04 1:44 ` [PATCH 10/32] wcn36xx: Use mem_to_flex_dup() with struct wcn36xx_hal_ind_msg Kees Cook
2022-05-04 5:42 ` Kalle Valo
2022-05-04 15:08 ` Kees Cook
2022-05-04 1:44 ` [PATCH 11/32] nl80211: Use mem_to_flex_dup() with struct cfg80211_cqm_config Kees Cook
2022-05-04 1:44 ` [PATCH 12/32] cfg80211: Use mem_to_flex_dup() with struct cfg80211_bss_ies Kees Cook
2022-05-04 7:28 ` Johannes Berg
2022-05-04 15:13 ` Kees Cook
2022-05-04 1:44 ` [PATCH 13/32] mac80211: Use mem_to_flex_dup() with several structs Kees Cook
2022-05-04 1:44 ` [PATCH 14/32] af_unix: Use mem_to_flex_dup() with struct unix_address Kees Cook
2022-05-04 1:44 ` [PATCH 15/32] 802/garp: Use mem_to_flex_dup() with struct garp_attr Kees Cook
2022-05-04 1:44 ` [PATCH 16/32] 802/mrp: Use mem_to_flex_dup() with struct mrp_attr Kees Cook
2022-05-04 1:44 ` [PATCH 17/32] net/flow_offload: Use mem_to_flex_dup() with struct flow_action_cookie Kees Cook
2022-05-04 1:44 ` [PATCH 18/32] firewire: Use __mem_to_flex_dup() with struct iso_interrupt_event Kees Cook
2022-05-04 1:44 ` [PATCH 19/32] afs: Use mem_to_flex_dup() with struct afs_acl Kees Cook
2022-05-04 1:44 ` [PATCH 20/32] ASoC: sigmadsp: Use mem_to_flex_dup() with struct sigmadsp_data Kees Cook
2022-05-04 15:17 ` Mark Brown
2022-05-04 1:44 ` [PATCH 21/32] soc: qcom: apr: Use mem_to_flex_dup() with struct apr_rx_buf Kees Cook
2022-05-04 1:44 ` [PATCH 22/32] atags_proc: Use mem_to_flex_dup() with struct buffer Kees Cook
2022-05-04 1:44 ` [PATCH 23/32] Bluetooth: Use mem_to_flex_dup() with struct hci_op_configure_data_path Kees Cook
2022-05-04 1:44 ` [PATCH 24/32] IB/hfi1: Use mem_to_flex_dup() for struct tid_rb_node Kees Cook
2022-05-04 1:44 ` [PATCH 25/32] Drivers: hv: utils: Use mem_to_flex_dup() with struct cn_msg Kees Cook
2022-05-04 1:44 ` [PATCH 26/32] ima: Use mem_to_flex_dup() with struct modsig Kees Cook
2022-05-04 1:44 ` [PATCH 27/32] KEYS: Use mem_to_flex_dup() with struct user_key_payload Kees Cook
2022-05-04 1:44 ` [PATCH 28/32] selinux: Use mem_to_flex_dup() with xfrm and sidtab Kees Cook
2022-05-04 22:57 ` Paul Moore
2022-05-04 23:43 ` Gustavo A. R. Silva
2022-05-05 3:14 ` Paul Moore
2022-05-05 18:39 ` Kees Cook
2022-05-05 23:16 ` Paul Moore
2022-05-06 1:08 ` Gustavo A. R. Silva [this message]
2022-05-04 1:44 ` [PATCH 29/32] xtensa: Use mem_to_flex_dup() with struct property Kees Cook
2022-05-04 18:09 ` Rob Herring
2022-05-04 1:44 ` [PATCH 30/32] usb: gadget: f_fs: Use mem_to_flex_dup() with struct ffs_buffer Kees Cook
2022-05-04 1:44 ` [PATCH 31/32] xenbus: Use mem_to_flex_dup() with struct read_buffer Kees Cook
2022-05-04 1:44 ` [PATCH 32/32] esas2r: Use __mem_to_flex() with struct atto_ioctl Kees Cook
2022-05-12 21:41 ` [PATCH 19/32] afs: Use mem_to_flex_dup() with struct afs_acl David Howells
2022-05-13 15:44 ` Kees Cook
2022-05-12 21:47 ` [PATCH 00/32] Introduce flexible array struct memcpy() helpers David Howells
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