[PATCH] libelf: If e_phnum is zero then set e_phoff also to zero.
Mark Wielaard
mjw at redhat.com
Wed May 13 13:25:27 UTC 2015
If phnum is zero make sure e_phoff is also zero and not some random value.
That would cause trouble in update_file. This could happen when ELF_F_LAYOUT
is set and the user copied over a ehdr from a bogus ELF file where the phdrs
are unreadable. In that case trying to write out the new ELF image would
crash trying to follow the bogus e_phdr value.
Signed-off-by: Mark Wielaard <mjw at redhat.com>
---
libelf/ChangeLog | 5 +++++
libelf/elf32_updatenull.c | 8 ++++++++
2 files changed, 13 insertions(+)
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 0b9b478..2d10b83 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-13 Mark Wielaard <mjw at redhat.com>
+
+ * elf32_updatenull.c (default_ehdr): If e_phnum is zero then set
+ e_phoff also to zero.
+
2015-05-12 Mark Wielaard <mjw at redhat.com>
* elf32_updatenull.c (updatenull_wrlock): Check that sh_addralign
diff --git a/libelf/elf32_updatenull.c b/libelf/elf32_updatenull.c
index a0de80e..c59ffcb 100644
--- a/libelf/elf32_updatenull.c
+++ b/libelf/elf32_updatenull.c
@@ -106,6 +106,14 @@ ELFW(default_ehdr,LIBELFBITS) (Elf *elf, ElfW2(LIBELFBITS,Ehdr) *ehdr,
elf->state.ELFW(elf,LIBELFBITS).ehdr_flags |= ELF_F_DIRTY;
}
+ /* If phnum is zero make sure e_phoff is also zero and not some random
+ value. That would cause trouble in update_file. */
+ if (ehdr->e_phnum == 0 && ehdr->e_phoff != 0)
+ {
+ ehdr->e_phoff = 0;
+ elf->state.ELFW(elf,LIBELFBITS).ehdr_flags |= ELF_F_DIRTY;
+ }
+
return 0;
}
--
2.1.0
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