i2cset: fix 'i' & 's' modes (3 extra bytes were sent)

When 'i' or 's' modes are selected block array is filled from offset 3
(blen = 3) but copied to data.block buffer from offset 0 so first 3 bytes
contains garbage from stack.
The buffer that is sent is also 3 bytes too long due to those extra 3
bytes.

Signed-off-by: Avi Fishman <AviFishman70@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 27 insertions, 13 deletions

diff --git a/miscutils/i2c_tools.c b/miscutils/i2c_tools.c
index fc392d9dc..82f9842bd 100644
--- a/miscutils/i2c_tools.c
+++ b/miscutils/i2c_tools.c
@@ -562,14 +562,19 @@ int i2cset_main(int argc, char **argv)
                               opt_m = (1 << 2), opt_r = (1 << 3);
 
         int bus_num, bus_addr, data_addr, mode = I2C_SMBUS_BYTE, pec = 0;
-        int val, blen = 0, mask = 0, fd, status;
+        int val, blen, mask, fd, status;
         unsigned char block[I2C_SMBUS_BLOCK_MAX];
         char *opt_m_arg = NULL;
         unsigned opts;
 
-        opts = getopt32(argv, "^" "fym:r" "\0" "-3"/*from 3 to ? args*/, &opt_m_arg);
+        opts = getopt32(argv, "^"
+                "fym:r"
+                "\0" "-3", /* minimum 3 args */
+                &opt_m_arg
+        );
         argv += optind;
         argc -= optind;
+        argc--; /* now argv[argc] is last arg */
 
         bus_num = i2c_bus_lookup(argv[0]);
         bus_addr = i2c_parse_bus_addr(argv[1]);
@@ -579,20 +584,26 @@ int i2cset_main(int argc, char **argv)
                 if (!argv[4] && argv[3][0] != 'c') {
                         mode = I2C_SMBUS_BYTE_DATA; /* Implicit b */
                 } else {
-                        switch (argv[argc-1][0]) {
-                        case 'c': /* Already set */                     break;
-                        case 'b': mode = I2C_SMBUS_BYTE_DATA;           break;
-                        case 'w': mode = I2C_SMBUS_WORD_DATA;           break;
-                        case 's': mode = I2C_SMBUS_BLOCK_DATA;          break;
-                        case 'i': mode = I2C_SMBUS_I2C_BLOCK_DATA;      break;
+                        switch (argv[argc][0]) {
+                        case 'c': /* Already set */
+                                break;
+                        case 'b': mode = I2C_SMBUS_BYTE_DATA;
+                                break;
+                        case 'w': mode = I2C_SMBUS_WORD_DATA;
+                                break;
+                        case 's': mode = I2C_SMBUS_BLOCK_DATA;
+                                break;
+                        case 'i': mode = I2C_SMBUS_I2C_BLOCK_DATA;
+                                break;
                         default:
                                 bb_error_msg("invalid mode");
                                 bb_show_usage();
                         }
 
-                        pec = argv[argc-1][1] == 'p';
-                        if (mode == I2C_SMBUS_BLOCK_DATA ||
-                                        mode == I2C_SMBUS_I2C_BLOCK_DATA) {
+                        pec = (argv[argc][1] == 'p');
+                        if (mode == I2C_SMBUS_BLOCK_DATA
+                         || mode == I2C_SMBUS_I2C_BLOCK_DATA
+                        ) {
                                 if (pec && mode == I2C_SMBUS_I2C_BLOCK_DATA)
                                         bb_error_msg_and_die(
                                                 "PEC not supported for I2C "
@@ -606,6 +617,8 @@ int i2cset_main(int argc, char **argv)
         }
 
         /* Prepare the value(s) to be written according to current mode. */
+        mask = 0;
+        blen = 0;
         switch (mode) {
         case I2C_SMBUS_BYTE_DATA:
                 val = xstrtou_range(argv[3], 0, 0, 0xff);
@@ -615,8 +628,9 @@ int i2cset_main(int argc, char **argv)
                 break;
         case I2C_SMBUS_BLOCK_DATA:
         case I2C_SMBUS_I2C_BLOCK_DATA:
-                for (blen = 3; blen < (argc - 1); blen++)
-                        block[blen] = xstrtou_range(argv[blen], 0, 0, 0xff);
+                for (blen = 3; blen < argc; blen++)
+                        block[blen - 3] = xstrtou_range(argv[blen], 0, 0, 0xff);
+                blen -= 3;
                 val = -1;
                 break;
         default: