lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 13 Feb 2023 13:52:45 +0100 From: Amadeusz Sławiński <amadeuszx.slawinski@...ux.intel.com> To: Kees Cook <keescook@...omium.org> Cc: Cezary Rojewski <cezary.rojewski@...el.com>, Sasa Ostrouska <casaxa@...il.com>, Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>, Liam Girdwood <liam.r.girdwood@...ux.intel.com>, Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>, Bard Liao <yung-chuan.liao@...ux.intel.com>, Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>, Kai Vehmanen <kai.vehmanen@...ux.intel.com>, Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, alsa-devel@...a-project.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] ASoC: Intel: Skylake: Replace 1-element array with flex-array On 2/10/2023 8:06 PM, Kees Cook wrote: > On Fri, Feb 10, 2023 at 02:10:56PM +0100, Amadeusz Sławiński wrote: >> On 2/10/2023 6:14 AM, Kees Cook wrote: >>> The kernel is globally removing the ambiguous 0-length and 1-element >>> arrays in favor of flexible arrays, so that we can gain both compile-time >>> and run-time array bounds checking[1]. In this instance, struct >>> skl_cpr_cfg contains struct skl_cpr_gtw_cfg, which defined "config_data" >>> as a 1-element array. >>> >>> Normally when switching from a 1-element array to a flex-array, any >>> related size calculations must be adjusted too. However, it seems the >>> original code was over-allocating space, since 1 extra u32 would be >>> included by the sizeof(): >>> >>> param_size = sizeof(struct skl_cpr_cfg); >>> param_size += mconfig->formats_config[SKL_PARAM_INIT].caps_size; >>> >>> But the copy uses caps_size bytes, and cap_size / 4 (i.e. sizeof(u32)) >>> for the length tracking: >>> >>> memcpy(cpr_mconfig->gtw_cfg.config_data, >>> mconfig->formats_config[SKL_PARAM_INIT].caps, >>> mconfig->formats_config[SKL_PARAM_INIT].caps_size); >>> >>> cpr_mconfig->gtw_cfg.config_length = >>> (mconfig->formats_config[SKL_PARAM_INIT].caps_size) / 4; >>> >>> Therefore, no size calculations need adjusting. Change the struct >>> skl_cpr_gtw_cfg config_data member to be a true flexible array, which >>> also fixes the over-allocation, and silences this memcpy run-time false >>> positive: >>> >>> memcpy: detected field-spanning write (size 100) of single field "cpr_mconfig->gtw_cfg.config_data" at sound/soc/intel/skylake/skl-messages.c:554 (size 4) >>> >>> [1] For lots of details, see both: >>> https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays >>> https://people.kernel.org/kees/bounded-flexible-arrays-in-c >>> >>> Reported-by: Sasa Ostrouska <casaxa@...il.com> >>> Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/ >>> Cc: Cezary Rojewski <cezary.rojewski@...el.com> >>> Cc: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com> >>> Cc: Liam Girdwood <liam.r.girdwood@...ux.intel.com> >>> Cc: Peter Ujfalusi <peter.ujfalusi@...ux.intel.com> >>> Cc: Bard Liao <yung-chuan.liao@...ux.intel.com> >>> Cc: Ranjani Sridharan <ranjani.sridharan@...ux.intel.com> >>> Cc: Kai Vehmanen <kai.vehmanen@...ux.intel.com> >>> Cc: Mark Brown <broonie@...nel.org> >>> Cc: Jaroslav Kysela <perex@...ex.cz> >>> Cc: Takashi Iwai <tiwai@...e.com> >>> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org> >>> Cc: "Amadeusz Sławiński" <amadeuszx.slawinski@...ux.intel.com> >>> Cc: alsa-devel@...a-project.org >>> Signed-off-by: Kees Cook <keescook@...omium.org> >>> --- >>> sound/soc/intel/skylake/skl-topology.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/sound/soc/intel/skylake/skl-topology.h b/sound/soc/intel/skylake/skl-topology.h >>> index 6db0fd7bad49..ad94f8020c27 100644 >>> --- a/sound/soc/intel/skylake/skl-topology.h >>> +++ b/sound/soc/intel/skylake/skl-topology.h >>> @@ -115,7 +115,7 @@ struct skl_cpr_gtw_cfg { >>> u32 dma_buffer_size; >>> u32 config_length; >>> /* not mandatory; required only for DMIC/I2S */ >>> - u32 config_data[1]; >>> + u32 config_data[]; >>> } __packed; >>> struct skl_dma_control { >> >> This fails in our validation. > > Ah, okay. Thanks for checking! > >> Maybe we can use the union workaround, to >> leave the size as is? >> >> Following seems to work in manual test: >> diff --git a/sound/soc/intel/skylake/skl-topology.h >> b/sound/soc/intel/skylake/skl-topology.h >> index 6db0fd7bad49..ffbd2e60fede 100644 >> --- a/sound/soc/intel/skylake/skl-topology.h >> +++ b/sound/soc/intel/skylake/skl-topology.h >> @@ -115,7 +115,10 @@ struct skl_cpr_gtw_cfg { >> u32 dma_buffer_size; >> u32 config_length; >> /* not mandatory; required only for DMIC/I2S */ >> - u32 config_data[1]; >> + union { >> + u32 x; >> + u32 config_data[0]; >> + }; > > Yeah, that could work, though the last member would be: > DECLARE_FLEX_ARRAY(u32, config_data); > otherwise the array is 0 length (rather than a proper flex array). > > But before that, let me see if I can track down where the size is being > used, in case we can avoid adding the padding. > I did spend some more time on this, apparently struct was missing one field according to IPC protocol. I've send fix for this.
Powered by blists - more mailing lists