[COMMITTED] libelf: Return error if elf_compress_gnu is used on SHF_COMPRESSED section.
Mark Wielaard
mark@klomp.org
Sat Aug 18 20:08:00 GMT 2018
Compressing a section that is already compressed is fine, but useless.
But it isn't possible to gnu compress (or decompress) a SHF_COMPRESSED
section since there is no state kept that would tell if the section was
first GNU compressed or first gabi compressed. Calling elf_compress_gnu
on a section and then calling elf_compress on it to decompress it twice
could cause a crash (the other way around is fine). Just disallow it.
https://sourceware.org/bugzilla/show_bug.cgi?id=23528
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
libelf/ChangeLog | 7 +++++++
libelf/elf_compress_gnu.c | 4 +++-
libelf/libelf.h | 5 +++++
3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 744c5b4d..7c884b00 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,10 @@
+2018-08-18 Mark Wielaard <mark@klomp.org>
+
+ * libelf.h (elf_compress_gnu): Add documentation about
+ interaction between SHF_COMPRESED and elf_compress_gnu.
+ * elf_compress_gnu.c (elf_compress_gnu): Return error if section
+ sh_flags has SHF_COMPRESSED set.
+
2018-07-27 Mark Wielaard <mark@klomp.org>
* libelf.h (elf_getshdrstrndx): Fix documentation.
diff --git a/libelf/elf_compress_gnu.c b/libelf/elf_compress_gnu.c
index c35dc395..dfa7c571 100644
--- a/libelf/elf_compress_gnu.c
+++ b/libelf/elf_compress_gnu.c
@@ -80,7 +80,9 @@ elf_compress_gnu (Elf_Scn *scn, int inflate, unsigned int flags)
sh_addralign = shdr->sh_addralign;
}
- if ((sh_flags & SHF_ALLOC) != 0)
+ /* Allocated sections, or sections that are already are compressed
+ cannot (also) be GNU compressed. */
+ if ((sh_flags & SHF_ALLOC) != 0 || (sh_flags & SHF_COMPRESSED))
{
__libelf_seterrno (ELF_E_INVALID_SECTION_FLAGS);
return -1;
diff --git a/libelf/libelf.h b/libelf/libelf.h
index 61f19231..d11358cc 100644
--- a/libelf/libelf.h
+++ b/libelf/libelf.h
@@ -366,6 +366,11 @@ extern Elf64_Chdr *elf64_getchdr (Elf_Scn *__scn);
It is an error to request compression for a section that already
has SHF_COMPRESSED set, or (for elf_compress) to request
decompression for an section that doesn't have SHF_COMPRESSED set.
+ If a section has SHF_COMPRESSED set then calling elf_compress_gnu
+ will result in an error. The section has to be decompressed first
+ using elf_compress. Calling elf_compress on a section compressed
+ with elf_compress_gnu is fine, but probably useless.
+
It is always an error to call these functions on SHT_NOBITS
sections or if the section has the SHF_ALLOC flag set.
elf_compress_gnu will not check whether the section name starts
--
2.18.0
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