[ethtool PATCH v3 04/12] ethtool.c: do_seeprom checks for params & stdin sanity

[David Decotigny <ddecotig@gmail.com>]

From: David Decotigny <decot@googlers.com>

Tested:
  On qemu e1000:
  $ dd if=/dev/zero bs=2 count=5 | /mnt/ethtool -E eth0 length 9
  too much data from stdin
  $ dd if=/dev/zero bs=2 count=5 | /mnt/ethtool -E eth0 length 11
  not enough data from stdin
  $ dd if=/dev/zero bs=2 count=5 | /mnt/ethtool -E eth0 length 10
  Cannot set EEPROM data: Bad address


Signed-off-by: David Decotigny <decot@googlers.com>
---
 ethtool.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/ethtool.c b/ethtool.c
index c64b962..19f479c 100644
--- a/ethtool.c
+++ b/ethtool.c
@@ -2828,8 +2828,14 @@ static int do_seeprom(struct cmd_context *ctx)
 	if (seeprom_length == -1)
 		seeprom_length = drvinfo.eedump_len;
 
-	if (drvinfo.eedump_len < seeprom_offset + seeprom_length)
-		seeprom_length = drvinfo.eedump_len - seeprom_offset;
+	if (drvinfo.eedump_len < seeprom_offset + seeprom_length) {
+		if (drvinfo.eedump_len > seeprom_offset)
+			seeprom_length = drvinfo.eedump_len - seeprom_offset;
+		else {
+			fprintf(stderr, "offset & length out of bounds\n");
+			return 75;
+		}
+	}
 
 	eeprom = calloc(1, sizeof(*eeprom)+seeprom_length);
 	if (!eeprom) {
@@ -2844,8 +2850,18 @@ static int do_seeprom(struct cmd_context *ctx)
 	eeprom->data[0] = seeprom_value;
 
 	/* Multi-byte write: read input from stdin */
-	if (!seeprom_value_seen)
-		eeprom->len = fread(eeprom->data, 1, eeprom->len, stdin);
+	if (!seeprom_value_seen) {
+		if (1 != fread(eeprom->data, eeprom->len, 1, stdin)) {
+			fprintf(stderr, "not enough data from stdin\n");
+			free(eeprom);
+			return 75;
+		}
+		if ((EOF != fgetc(stdin)) || !feof(stdin)) {
+			fprintf(stderr, "too much data from stdin\n");
+			free(eeprom);
+			return 75;
+		}
+	}
 
 	err = send_ioctl(ctx, eeprom);
 	if (err < 0) {
-- 
2.7.0.rc3.207.g0ac5344