* [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838]
@ 2022-01-31 15:24 H.J. Lu
2022-01-31 15:39 ` Florian Weimer
2022-01-31 22:19 ` Michael Hudson-Doyle
0 siblings, 2 replies; 5+ messages in thread
From: H.J. Lu @ 2022-01-31 15:24 UTC (permalink / raw)
To: libc-alpha; +Cc: Florian Weimer, Carlos O'Donell, Michael Hudson-Doyle
commit 163f625cf9becbb82dfec63a29e566324129c0cd
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Tue Dec 21 12:35:47 2021 -0800
elf: Remove excessive p_align check on PT_LOAD segments [BZ #28688]
removed the p_align check against the page size. It caused the loader
crash in shared objects with the invalid p_align. Update _dl_map_segments
to detect invalid holes. This fixes BZ #28838.
---
elf/dl-map-segments.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index 172692b120..fd24cf5d01 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -113,6 +113,9 @@ _dl_map_segments (struct link_map *l, int fd,
unallocated. Then jump into the normal segment-mapping loop to
handle the portion of the segment past the end of the file
mapping. */
+ if (__glibc_unlikely (loadcmds[nloadcmds - 1].mapstart <
+ c->mapend))
+ return N_("ELF load command address/offset not page-aligned");
if (__glibc_unlikely
(__mprotect ((caddr_t) (l->l_addr + c->mapend),
loadcmds[nloadcmds - 1].mapstart - c->mapend,
--
2.34.1
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] 2022-01-31 15:24 [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] H.J. Lu @ 2022-01-31 15:39 ` Florian Weimer 2022-01-31 15:59 ` H.J. Lu 2022-01-31 16:07 ` H.J. Lu 2022-01-31 22:19 ` Michael Hudson-Doyle 1 sibling, 2 replies; 5+ messages in thread From: Florian Weimer @ 2022-01-31 15:39 UTC (permalink / raw) To: H.J. Lu; +Cc: libc-alpha, Carlos O'Donell, Michael Hudson-Doyle * H. J. Lu: > commit 163f625cf9becbb82dfec63a29e566324129c0cd > Author: H.J. Lu <hjl.tools@gmail.com> > Date: Tue Dec 21 12:35:47 2021 -0800 > > elf: Remove excessive p_align check on PT_LOAD segments [BZ #28688] > > removed the p_align check against the page size. It caused the loader > crash in shared objects with the invalid p_align. Update _dl_map_segments > to detect invalid holes. This fixes BZ #28838. Commit message should reference commit ID and mention the failing test/module name. > --- > elf/dl-map-segments.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h > index 172692b120..fd24cf5d01 100644 > --- a/elf/dl-map-segments.h > +++ b/elf/dl-map-segments.h > @@ -113,6 +113,9 @@ _dl_map_segments (struct link_map *l, int fd, > unallocated. Then jump into the normal segment-mapping loop to > handle the portion of the segment past the end of the file > mapping. */ > + if (__glibc_unlikely (loadcmds[nloadcmds - 1].mapstart < > + c->mapend)) > + return N_("ELF load command address/offset not page-aligned"); > if (__glibc_unlikely > (__mprotect ((caddr_t) (l->l_addr + c->mapend), > loadcmds[nloadcmds - 1].mapstart - c->mapend, This seems to be fairly risky because I don't think that so far, we enforce increasing LOAD segment addresses (although required by te EHF specification). Given LDFLAGS-tst-p_alignmod3.so += -Wl,-z,max-page-size=0x100,-z,common-page-size=0x100 and RELRO construction for that .../elf/tst-p_alignmod3.so: cannot change memory protections seems to be a valid failure string for this test. However, worst case, there could be a different kind of failure, if the RELRO mprotect start is page-aligned by chance, and the kernel rounds up the end address to a page boundary. The RELRO protection then covers more than what the link editor expected, and this can cause crashes later on. But this isn't something we can detect easily, I think. Thanks, Florian ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] 2022-01-31 15:39 ` Florian Weimer @ 2022-01-31 15:59 ` H.J. Lu 2022-01-31 16:07 ` H.J. Lu 1 sibling, 0 replies; 5+ messages in thread From: H.J. Lu @ 2022-01-31 15:59 UTC (permalink / raw) To: Florian Weimer; +Cc: GNU C Library, Carlos O'Donell, Michael Hudson-Doyle On Mon, Jan 31, 2022 at 7:40 AM Florian Weimer <fweimer@redhat.com> wrote: > > * H. J. Lu: > > > commit 163f625cf9becbb82dfec63a29e566324129c0cd > > Author: H.J. Lu <hjl.tools@gmail.com> > > Date: Tue Dec 21 12:35:47 2021 -0800 > > > > elf: Remove excessive p_align check on PT_LOAD segments [BZ #28688] > > > > removed the p_align check against the page size. It caused the loader > > crash in shared objects with the invalid p_align. Update _dl_map_segments > > to detect invalid holes. This fixes BZ #28838. > > Commit message should reference commit ID and mention the failing > test/module name. > > > --- > > elf/dl-map-segments.h | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h > > index 172692b120..fd24cf5d01 100644 > > --- a/elf/dl-map-segments.h > > +++ b/elf/dl-map-segments.h > > @@ -113,6 +113,9 @@ _dl_map_segments (struct link_map *l, int fd, > > unallocated. Then jump into the normal segment-mapping loop to > > handle the portion of the segment past the end of the file > > mapping. */ > > + if (__glibc_unlikely (loadcmds[nloadcmds - 1].mapstart < > > + c->mapend)) > > + return N_("ELF load command address/offset not page-aligned"); > > if (__glibc_unlikely > > (__mprotect ((caddr_t) (l->l_addr + c->mapend), > > loadcmds[nloadcmds - 1].mapstart - c->mapend, ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ If loadcmds[nloadcmds - 1].mapstart < c->mapend, the length argument passed to __mprotect is a huge number and invalid. > > This seems to be fairly risky because I don't think that so far, we > enforce increasing LOAD segment addresses (although required by te EHF > specification). > > Given > > LDFLAGS-tst-p_alignmod3.so += -Wl,-z,max-page-size=0x100,-z,common-page-size=0x100 > > and RELRO construction for that > > .../elf/tst-p_alignmod3.so: cannot change memory protections > > seems to be a valid failure string for this test. However, worst case, > there could be a different kind of failure, if the RELRO mprotect start > is page-aligned by chance, and the kernel rounds up the end address to a > page boundary. The RELRO protection then covers more than what the link > editor expected, and this can cause crashes later on. But this isn't > something we can detect easily, I think. > > Thanks, > Florian > -- H.J. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] 2022-01-31 15:39 ` Florian Weimer 2022-01-31 15:59 ` H.J. Lu @ 2022-01-31 16:07 ` H.J. Lu 1 sibling, 0 replies; 5+ messages in thread From: H.J. Lu @ 2022-01-31 16:07 UTC (permalink / raw) To: Florian Weimer; +Cc: GNU C Library, Carlos O'Donell, Michael Hudson-Doyle On Mon, Jan 31, 2022 at 7:40 AM Florian Weimer <fweimer@redhat.com> wrote: > > * H. J. Lu: > > > commit 163f625cf9becbb82dfec63a29e566324129c0cd > > Author: H.J. Lu <hjl.tools@gmail.com> > > Date: Tue Dec 21 12:35:47 2021 -0800 > > > > elf: Remove excessive p_align check on PT_LOAD segments [BZ #28688] > > > > removed the p_align check against the page size. It caused the loader > > crash in shared objects with the invalid p_align. Update _dl_map_segments > > to detect invalid holes. This fixes BZ #28838. > > Commit message should reference commit ID and mention the failing > test/module name. How about this? commit 163f625cf9becbb82dfec63a29e566324129c0cd Author: H.J. Lu <hjl.tools@gmail.com> Date: Tue Dec 21 12:35:47 2021 -0800 elf: Remove excessive p_align check on PT_LOAD segments [BZ #28688] removed the p_align check against the page size. It caused the loader crash on elf/tst-p_align3 when loading elf/tst-p_alignmod3.so, which has the invalid p_align in PT_LOAD segments, added by commit d8d94863ef125a392b929732b37e07dc927fbcd1 Author: H.J. Lu <hjl.tools@gmail.com> Date: Tue Dec 21 13:42:28 2021 -0800 The loader crash is random, depending on architecture and toolchain. Update _dl_map_segments to detect invalid holes. This fixes BZ #28838. > > --- > > elf/dl-map-segments.h | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h > > index 172692b120..fd24cf5d01 100644 > > --- a/elf/dl-map-segments.h > > +++ b/elf/dl-map-segments.h > > @@ -113,6 +113,9 @@ _dl_map_segments (struct link_map *l, int fd, > > unallocated. Then jump into the normal segment-mapping loop to > > handle the portion of the segment past the end of the file > > mapping. */ > > + if (__glibc_unlikely (loadcmds[nloadcmds - 1].mapstart < > > + c->mapend)) > > + return N_("ELF load command address/offset not page-aligned"); > > if (__glibc_unlikely > > (__mprotect ((caddr_t) (l->l_addr + c->mapend), > > loadcmds[nloadcmds - 1].mapstart - c->mapend, > > This seems to be fairly risky because I don't think that so far, we > enforce increasing LOAD segment addresses (although required by te EHF > specification). > > Given > > LDFLAGS-tst-p_alignmod3.so += -Wl,-z,max-page-size=0x100,-z,common-page-size=0x100 > > and RELRO construction for that > > .../elf/tst-p_alignmod3.so: cannot change memory protections > > seems to be a valid failure string for this test. However, worst case, > there could be a different kind of failure, if the RELRO mprotect start > is page-aligned by chance, and the kernel rounds up the end address to a > page boundary. The RELRO protection then covers more than what the link > editor expected, and this can cause crashes later on. But this isn't > something we can detect easily, I think. > > Thanks, > Florian > -- H.J. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] 2022-01-31 15:24 [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] H.J. Lu 2022-01-31 15:39 ` Florian Weimer @ 2022-01-31 22:19 ` Michael Hudson-Doyle 1 sibling, 0 replies; 5+ messages in thread From: Michael Hudson-Doyle @ 2022-01-31 22:19 UTC (permalink / raw) To: H.J. Lu; +Cc: libc-alpha, Florian Weimer, Carlos O'Donell On Tue, 1 Feb 2022 at 04:24, H.J. Lu <hjl.tools@gmail.com> wrote: > commit 163f625cf9becbb82dfec63a29e566324129c0cd > Author: H.J. Lu <hjl.tools@gmail.com> > Date: Tue Dec 21 12:35:47 2021 -0800 > > elf: Remove excessive p_align check on PT_LOAD segments [BZ #28688] > > removed the p_align check against the page size. It caused the loader > crash in shared objects with the invalid p_align. Update _dl_map_segments > to detect invalid holes. This fixes BZ #28838. > I am not competent to have an opinion on the correctness of the change, but the test passes on Launchapd's i386 and amd64 builders with it. Cheers, mwh > --- > elf/dl-map-segments.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h > index 172692b120..fd24cf5d01 100644 > --- a/elf/dl-map-segments.h > +++ b/elf/dl-map-segments.h > @@ -113,6 +113,9 @@ _dl_map_segments (struct link_map *l, int fd, > unallocated. Then jump into the normal segment-mapping loop > to > handle the portion of the segment past the end of the file > mapping. */ > + if (__glibc_unlikely (loadcmds[nloadcmds - 1].mapstart < > + c->mapend)) > + return N_("ELF load command address/offset not page-aligned"); > if (__glibc_unlikely > (__mprotect ((caddr_t) (l->l_addr + c->mapend), > loadcmds[nloadcmds - 1].mapstart - c->mapend, > -- > 2.34.1 > > ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-01-31 22:19 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-01-31 15:24 [PATCH] elf: Check invalid hole in PT_LOAD segments [BZ #28838] H.J. Lu 2022-01-31 15:39 ` Florian Weimer 2022-01-31 15:59 ` H.J. Lu 2022-01-31 16:07 ` H.J. Lu 2022-01-31 22:19 ` Michael Hudson-Doyle
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