* Re: Limited/Broken functionality of ASLR for Libs >= 2MB [not found] ` <ZaWZqnD7XmP5HMA0@casper.infradead.org> @ 2024-01-16 8:09 ` Ard Biesheuvel 2024-01-23 22:35 ` Kees Cook 0 siblings, 1 reply; 4+ messages in thread From: Ard Biesheuvel @ 2024-01-16 8:09 UTC (permalink / raw) To: Matthew Wilcox, Kees Cook, Linux ARM Cc: mail, linux-hardening, Jakub Wilk, Salvatore Bonaccorso, Linux Memory Management List, William Kucharski (cc Kees, LAKML) https://lkml.kernel.org/r/69fa6015256613ed10aee996e181ebd4%40horotw.com On Mon, 15 Jan 2024 at 21:46, Matthew Wilcox <willy@infradead.org> wrote: > ... > Yeah, I don't know either. Outside my scope of expertise. > > I received a suggestion off-list that we only do the PMD alignment on > 64-bit, which seems quite reasonable to me. After all, I don't care > about performance on 32-bit just as much as I don't care about security > on 32-bit. > For context, the culprit is commit 1854bc6e2420472676c5c90d3d6b15f6cd640e40 Author: William Kucharski <william.kucharski@oracle.com> Date: Sun Sep 22 08:43:15 2019 -0400 mm/readahead: Align file mappings for non-DAX When we have the opportunity to use PMDs to map a file, we want to follow the same rules as DAX. Signed-off-by: William Kucharski <william.kucharski@oracle.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> which affects *all* 32-bit architectures not just i686. 32-bit ARM user space is still being deployed widely, even on arm64 Chromebooks running 64-bit kernels (at least up until recently) so unfortunately, we're not quite at the point yet where we can just let it rot. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Limited/Broken functionality of ASLR for Libs >= 2MB 2024-01-16 8:09 ` Limited/Broken functionality of ASLR for Libs >= 2MB Ard Biesheuvel @ 2024-01-23 22:35 ` Kees Cook 2024-01-24 1:04 ` Yang Shi 0 siblings, 1 reply; 4+ messages in thread From: Kees Cook @ 2024-01-23 22:35 UTC (permalink / raw) To: Ard Biesheuvel Cc: Matthew Wilcox, Linux ARM, mail, linux-hardening, Jakub Wilk, Salvatore Bonaccorso, Linux Memory Management List, William Kucharski On Tue, Jan 16, 2024 at 09:09:45AM +0100, Ard Biesheuvel wrote: > (cc Kees, LAKML) > > https://lkml.kernel.org/r/69fa6015256613ed10aee996e181ebd4%40horotw.com > > On Mon, 15 Jan 2024 at 21:46, Matthew Wilcox <willy@infradead.org> wrote: > > > ... > > Yeah, I don't know either. Outside my scope of expertise. > > > > I received a suggestion off-list that we only do the PMD alignment on > > 64-bit, which seems quite reasonable to me. After all, I don't care > > about performance on 32-bit just as much as I don't care about security > > on 32-bit. > > > > For context, the culprit is > > commit 1854bc6e2420472676c5c90d3d6b15f6cd640e40 > Author: William Kucharski <william.kucharski@oracle.com> > Date: Sun Sep 22 08:43:15 2019 -0400 > > mm/readahead: Align file mappings for non-DAX > > When we have the opportunity to use PMDs to map a file, we want to follow > the same rules as DAX. > > Signed-off-by: William Kucharski <william.kucharski@oracle.com> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > > which affects *all* 32-bit architectures not just i686. 32-bit ARM > user space is still being deployed widely, even on arm64 Chromebooks > running 64-bit kernels (at least up until recently) so unfortunately, > we're not quite at the point yet where we can just let it rot. Is this related at all to this thread as well? https://lore.kernel.org/lkml/20220809142457.4751229f@imladris.surriel.com/ Can we avoid this on 32-bit or at least not mislead userspace about the available entropy visible in /proc/sys/vm/mmap_rnd*_bits ? -Kees -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Limited/Broken functionality of ASLR for Libs >= 2MB 2024-01-23 22:35 ` Kees Cook @ 2024-01-24 1:04 ` Yang Shi 2024-01-24 16:08 ` Kees Cook 0 siblings, 1 reply; 4+ messages in thread From: Yang Shi @ 2024-01-24 1:04 UTC (permalink / raw) To: Kees Cook Cc: Ard Biesheuvel, Matthew Wilcox, Linux ARM, mail, linux-hardening, Jakub Wilk, Salvatore Bonaccorso, Linux Memory Management List, William Kucharski On Tue, Jan 23, 2024 at 2:37 PM Kees Cook <keescook@chromium.org> wrote: > > On Tue, Jan 16, 2024 at 09:09:45AM +0100, Ard Biesheuvel wrote: > > (cc Kees, LAKML) > > > > https://lkml.kernel.org/r/69fa6015256613ed10aee996e181ebd4%40horotw.com > > > > On Mon, 15 Jan 2024 at 21:46, Matthew Wilcox <willy@infradead.org> wrote: > > > > > ... > > > Yeah, I don't know either. Outside my scope of expertise. > > > > > > I received a suggestion off-list that we only do the PMD alignment on > > > 64-bit, which seems quite reasonable to me. After all, I don't care > > > about performance on 32-bit just as much as I don't care about security > > > on 32-bit. > > > > > > > For context, the culprit is > > > > commit 1854bc6e2420472676c5c90d3d6b15f6cd640e40 > > Author: William Kucharski <william.kucharski@oracle.com> > > Date: Sun Sep 22 08:43:15 2019 -0400 > > > > mm/readahead: Align file mappings for non-DAX > > > > When we have the opportunity to use PMDs to map a file, we want to follow > > the same rules as DAX. > > > > Signed-off-by: William Kucharski <william.kucharski@oracle.com> > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > > > > which affects *all* 32-bit architectures not just i686. 32-bit ARM > > user space is still being deployed widely, even on arm64 Chromebooks > > running 64-bit kernels (at least up until recently) so unfortunately, > > we're not quite at the point yet where we can just let it rot. > > Is this related at all to this thread as well? > https://lore.kernel.org/lkml/20220809142457.4751229f@imladris.surriel.com/ Yes > > Can we avoid this on 32-bit or at least not mislead userspace about the > available entropy visible in /proc/sys/vm/mmap_rnd*_bits ? https://lore.kernel.org/linux-mm/20240118133504.2910955-1-shy828301@gmail.com/ This patch basically made thp_get_unmapped_area no-op on 32 bit. > > -Kees > > -- > Kees Cook > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Limited/Broken functionality of ASLR for Libs >= 2MB 2024-01-24 1:04 ` Yang Shi @ 2024-01-24 16:08 ` Kees Cook 0 siblings, 0 replies; 4+ messages in thread From: Kees Cook @ 2024-01-24 16:08 UTC (permalink / raw) To: Yang Shi Cc: Ard Biesheuvel, Matthew Wilcox, Linux ARM, mail, linux-hardening, Jakub Wilk, Salvatore Bonaccorso, Linux Memory Management List, William Kucharski On Tue, Jan 23, 2024 at 05:04:22PM -0800, Yang Shi wrote: > On Tue, Jan 23, 2024 at 2:37 PM Kees Cook <keescook@chromium.org> wrote: > > > > On Tue, Jan 16, 2024 at 09:09:45AM +0100, Ard Biesheuvel wrote: > > > (cc Kees, LAKML) > > > > > > https://lkml.kernel.org/r/69fa6015256613ed10aee996e181ebd4%40horotw.com > > > > > > On Mon, 15 Jan 2024 at 21:46, Matthew Wilcox <willy@infradead.org> wrote: > > > > > > > ... > > > > Yeah, I don't know either. Outside my scope of expertise. > > > > > > > > I received a suggestion off-list that we only do the PMD alignment on > > > > 64-bit, which seems quite reasonable to me. After all, I don't care > > > > about performance on 32-bit just as much as I don't care about security > > > > on 32-bit. > > > > > > > > > > For context, the culprit is > > > > > > commit 1854bc6e2420472676c5c90d3d6b15f6cd640e40 > > > Author: William Kucharski <william.kucharski@oracle.com> > > > Date: Sun Sep 22 08:43:15 2019 -0400 > > > > > > mm/readahead: Align file mappings for non-DAX > > > > > > When we have the opportunity to use PMDs to map a file, we want to follow > > > the same rules as DAX. > > > > > > Signed-off-by: William Kucharski <william.kucharski@oracle.com> > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > > > > > > which affects *all* 32-bit architectures not just i686. 32-bit ARM > > > user space is still being deployed widely, even on arm64 Chromebooks > > > running 64-bit kernels (at least up until recently) so unfortunately, > > > we're not quite at the point yet where we can just let it rot. > > > > Is this related at all to this thread as well? > > https://lore.kernel.org/lkml/20220809142457.4751229f@imladris.surriel.com/ > > Yes > > > > > Can we avoid this on 32-bit or at least not mislead userspace about the > > available entropy visible in /proc/sys/vm/mmap_rnd*_bits ? > > https://lore.kernel.org/linux-mm/20240118133504.2910955-1-shy828301@gmail.com/ > > This patch basically made thp_get_unmapped_area no-op on 32 bit. Ah-ha! Okay, thanks very much. I missed this landing. :) -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-01-16 8:09 ` Limited/Broken functionality of ASLR for Libs >= 2MB Ard Biesheuvel
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2024-01-24 1:04 ` Yang Shi
2024-01-24 16:08 ` Kees Cook
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