elf/tst-big-note: Improve accuracy of test [BZ #20419]

It is possible that the link editor injects an allocated ABI tag note
before the artificial, allocated large note in the test.  Note parsing
in open_verify stops when the first ABI tag note is encountered, so if
the ABI tag note comes first, the problematic code is not actually
exercised.

Also tweak the artificial note so that it is a syntactically valid
4-byte aligned note, in case the link editor tries to parse notes and
process them.

Improves the testing part of commit 0065aaaaae51cd60210ec3a7e13.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

diff --git a/ChangeLog b/ChangeLog
index 85506efc998c82e7235cf271f1cc25ccdb7e7dc7..1ca155ebfc41fb69f58094fe96fccd6d23592e82 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-03-01  Florian Weimer  <fweimer@redhat.com>
+
+       [BZ #20419]
+       * elf/tst-big-note-lib.S: Create a syntactically valid note.
+       * elf/Makefile (tst-big-note-lib.so): Do not link with startup
+       code, to avoid creating an ABI tag note.
+       (modules-names-nobuild): Add tst-big-note-lib.
+
 2019-03-01  Stefan Liebler  <stli@linux.ibm.com>
 
        * sysdeps/s390/wcscpy-vx.S: Add strong aliases to

diff --git a/elf/Makefile b/elf/Makefile
index 55204073a31a4f77666ba16f151900c7eb8d050f..310a37cc13d6c2f1317af2c36975473005091913 100644 (file)
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -316,8 +316,8 @@ endif
 modules-execstack-yes = tst-execstack-mod
 extra-test-objs += $(addsuffix .os,$(strip $(modules-names)))
 
-# filtmod1.so has a special rule
-modules-names-nobuild := filtmod1
+# filtmod1.so, tst-big-note-lib.so have special rules.
+modules-names-nobuild := filtmod1 tst-big-note-lib
 
 tests += $(tests-static)
 
@@ -1515,6 +1515,11 @@ tst-libc_dlvsym-static-ENV = \
 $(objpfx)tst-libc_dlvsym-static.out: $(objpfx)tst-libc_dlvsym-dso.so
 
 $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so
+# Avoid creating an ABI tag note, which may come before the
+# artificial, large note in tst-big-note-lib.o and invalidate the
+# test.
+$(objpfx)tst-big-note-lib.so: $(objpfx)tst-big-note-lib.o
+       $(LINK.o) -shared -o $@ $(LDFLAGS.so) $<
 
 $(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so
 

diff --git a/elf/tst-big-note-lib.S b/elf/tst-big-note-lib.S
index e2008cf4aee134aa6e130907af07511ae63c5a36..721686fa0e87feecf516bc51e13eb18ce1bee276 100644 (file)
--- a/elf/tst-big-note-lib.S
+++ b/elf/tst-big-note-lib.S
@@ -20,7 +20,13 @@
    On a typical Linux system with 8MiB "ulimit -s", that was enough
    to trigger stack overflow in open_verify.  */
 
+#define NOTE_SIZE 8*1024*1024
+
 .pushsection .note.big,"a"
-.balign 4
-.fill 8*1024*1024, 1, 0
+       .balign 4
+       .long 5                 /* n_namesz.  Length of "GLIBC".  */
+       .long NOTE_SIZE         /* n_descsz.  */
+       .long 0                 /* n_type.  */
+       .ascii "GLIBC\0\0\0"    /* Name and alignment to four bytes.  */
+       .fill NOTE_SIZE, 1, 0
 .popsection