elf: Check invalid hole in PT_LOAD segments [BZ #28838]

Changes in v2:

1. Update commit log.

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
error or 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 failure caused by a negative length passed to __mprotect is
random, depending on architecture and toolchain.  Update _dl_map_segments
to detect invalid holes.  This fixes BZ #28838.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index b3513e7..024175b 100644 (file)
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -112,6 +112,9 @@ _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,