* [PATCH] libelf: Add n_namesz offset overflow check to gelf_get_note.
@ 2019-05-01 13:56 Mark Wielaard
2019-05-04 19:57 ` Mark Wielaard
0 siblings, 1 reply; 2+ messages in thread
From: Mark Wielaard @ 2019-05-01 13:56 UTC (permalink / raw)
To: elfutils-devel; +Cc: Mark Wielaard
During fuzzing of the new xlate_notes testcase I noticed that
gelf_get_note didn't check whether the n_namesz of a note was
too big. This could lead to offset wrapping around. Causing an
infinite loop going over all ELF notes. Fix by adding an overflow
check before updating offset.
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
libelf/ChangeLog | 5 +++++
libelf/gelf_getnote.c | 5 +++--
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 5eadaf7..924ff59 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2019-05-01 Mark Wielaard <mark@klomp.org>
+
+ * gelf_getnote.c (gelf_getnote): Check n_namesz doesn't overflow
+ offset.
+
2019-04-30 Mark Wielaard <mark@klomp.org>
* note_xlate.h (elf_cvt_note): Indicate we only translated the note
diff --git a/libelf/gelf_getnote.c b/libelf/gelf_getnote.c
index 6d33b35..0f7b9d6 100644
--- a/libelf/gelf_getnote.c
+++ b/libelf/gelf_getnote.c
@@ -80,11 +80,12 @@ gelf_getnote (Elf_Data *data, size_t offset, GElf_Nhdr *result,
the offset, after adding the namesz, and include padding
in descsz to get to the end. */
*name_offset = offset;
- offset += n->n_namesz;
- if (offset > data->d_size)
+ if (n->n_namesz > data->d_size
+ || offset > data->d_size - n->n_namesz)
offset = 0;
else
{
+ offset += n->n_namesz;
/* Include padding. Check below for overflow. */
GElf_Word descsz = (data->d_type == ELF_T_NHDR8
? NOTE_ALIGN8 (n->n_descsz)
--
1.8.3.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] libelf: Add n_namesz offset overflow check to gelf_get_note.
2019-05-01 13:56 [PATCH] libelf: Add n_namesz offset overflow check to gelf_get_note Mark Wielaard
@ 2019-05-04 19:57 ` Mark Wielaard
0 siblings, 0 replies; 2+ messages in thread
From: Mark Wielaard @ 2019-05-04 19:57 UTC (permalink / raw)
To: elfutils-devel
On Wed, May 01, 2019 at 03:55:59PM +0200, Mark Wielaard wrote:
> During fuzzing of the new xlate_notes testcase I noticed that
> gelf_get_note didn't check whether the n_namesz of a note was
> too big. This could lead to offset wrapping around. Causing an
> infinite loop going over all ELF notes. Fix by adding an overflow
> check before updating offset.
Pushed to master.
^ permalink raw reply [flat|nested] 2+ messages in thread
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