[Crash-utility] [PATCH] netdump: bugfix for read elf header

[Qianli Zhao]

From: Qianli Zhao <zhaoqianli at xiaomi.com>

Without the patch,errors may occur in reading the ELF header,
causing the parsing to fail.

Signed-off-by: Qianli Zhao <zhaoqianli at xiaomi.com>
---
When i use crash to parsing a kdump,i got below error.
This error occurs because of the read header less then SAFE_NETDUMP_ELF_HEADER_SIZE,
But can read MIN_NETDUMP_ELF_HEADER_SIZE bytes from the file correctly.
this issue is introduced due to commit:f42db6a33f0e0652df7cce8506352745b4794287

crash 7.2.9
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/var/tmp/ramdump_elf_B2R4cQ: ELF header read: No such file or directory
crash: malformed ELF file: /var/tmp/ramdump_elf_B2R4cQ

Usage:

  crash [OPTION]... NAMELIST MEMORY-IMAGE[@ADDRESS]	(dumpfile form)
  crash [OPTION]... [NAMELIST]             		(live system form)

Enter "crash -h" for details.

---
 netdump.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/netdump.c b/netdump.c
index c76d9dd..cb0af41 100644
--- a/netdump.c
+++ b/netdump.c
@@ -142,7 +142,7 @@ is_netdump(char *file, ulong source_query)
 		if (!read_flattened_format(fd, 0, eheader, size))
 			goto bailout;
 	} else {
-		if (read(fd, eheader, size) != size) {
+		if (read(fd, eheader, size) < MIN_NETDUMP_ELF_HEADER_SIZE) {
 			sprintf(buf, "%s: ELF header read", file);
 			perror(buf);
 			goto bailout;
-- 
2.7.4