[Crash-utility] [PATCH 1/2] netdump: fix illegal read to already freed buffer

[HATAYAMA Daisuke]

This issue was detected by valgrind as follows:

    ==1212== Invalid read of size 8
    ==1212==    at 0x56C400: resize_elf_header (netdump.c:585)
    ==1212==    by 0x56C400: is_netdump (netdump.c:363)
    ==1212==    by 0x463571: main (main.c:561)
    ==1212==  Address 0x4e8ec10 is 32 bytes inside a block of size 304 free'd
    ==1212==    at 0x483BCE8: realloc (vg_replace_malloc.c:834)
    ==1212==    by 0x56C393: resize_elf_header (netdump.c:547)
    ==1212==    by 0x56C393: is_netdump (netdump.c:363)
    ==1212==    by 0x463571: main (main.c:561)
    ==1212==  Block was alloc'd at
    ==1212==    at 0x4839809: malloc (vg_replace_malloc.c:307)
    ==1212==    by 0x56C078: is_netdump (netdump.c:136)
    ==1212==    by 0x463571: main (main.c:561)
    ==1212==

The issue was introduced by the commit
f42db6a33f0e0652df7cce8506352745b4794287 (Support core files with
"unusual" layout).

In resize_elf_header(), both elf32 and elf64 refer to the same address
as eheader, but when reallocating the address pointed at by eheader,
elf32 and elf64 are not updated, resulting in referring to the already
freed address.

To fix this issue, let's update elf32 and elf64 at the realloc().

Signed-off-by: HATAYAMA Daisuke <d.hatayama at fujitsu.com>
---
 netdump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/netdump.c b/netdump.c
index 2ca39e2..690f45e 100644
--- a/netdump.c
+++ b/netdump.c
@@ -550,6 +550,9 @@ resize_elf_header(int fd, char *file, char **eheader_ptr, char **sect0_ptr,
 	} else
 		*eheader_ptr = eheader;
 
+	elf32 = (Elf32_Ehdr *)&eheader[0];
+	elf64 = (Elf64_Ehdr *)&eheader[0];
+
 	if (FLAT_FORMAT()) {
 		if (!read_flattened_format(fd, 0, eheader, header_size))
 			return 0;
-- 
2.29.2