dd: fail if swab is attempted on odd-sized block

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/coreutils/dd.c b/coreutils/dd.c
index d6aa5ef..e229388 100644 (file)
--- a/coreutils/dd.c
+++ b/coreutils/dd.c
@@ -151,13 +151,13 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
        enum {
                /* Must be in the same order as OP_conv_XXX! */
                /* (see "flags |= (1 << what)" below) */
-               FLAG_NOTRUNC = 1 << 0,
-               FLAG_SYNC    = 1 << 1,
-               FLAG_NOERROR = 1 << 2,
-               FLAG_FSYNC   = 1 << 3,
-               FLAG_SWAB    = 1 << 4,
+               FLAG_NOTRUNC = (1 << 0) * ENABLE_FEATURE_DD_IBS_OBS,
+               FLAG_SYNC    = (1 << 1) * ENABLE_FEATURE_DD_IBS_OBS,
+               FLAG_NOERROR = (1 << 2) * ENABLE_FEATURE_DD_IBS_OBS,
+               FLAG_FSYNC   = (1 << 3) * ENABLE_FEATURE_DD_IBS_OBS,
+               FLAG_SWAB    = (1 << 4) * ENABLE_FEATURE_DD_IBS_OBS,
                /* end of conv flags */
-               FLAG_TWOBUFS = 1 << 5,
+               FLAG_TWOBUFS = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
                FLAG_COUNT   = 1 << 6,
        };
        static const char keywords[] ALIGN1 =
@@ -202,7 +202,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
        //swab          swap every pair of input bytes: will abort on non-even reads
 #endif
        };
-       int exitcode = EXIT_FAILURE;
+       smallint exitcode = EXIT_FAILURE;
        size_t ibs = 512, obs = 512;
        int i;
        char *ibuf, *obuf;
@@ -210,12 +210,14 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
        struct {
                int flags;
                size_t oc;
+               ssize_t prev_read_size; /* for detecting swab failure */
                off_t count;
                off_t seek, skip;
                const char *infile, *outfile;
        } Z;
 #define flags   (Z.flags  )
 #define oc      (Z.oc     )
+#define prev_read_size (Z.prev_read_size)
 #define count   (Z.count  )
 #define seek    (Z.seek   )
 #define skip    (Z.skip   )
@@ -381,14 +383,23 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
                        n = 0;
                }
                if (flags & FLAG_SWAB) {
-                       /* If n is odd, last byte is not swapped:
+                       uint16_t *p16, *end;
+
+                       /* Our code allows only last read to be odd-sized */
+                       if (prev_read_size & 1)
+                               bb_error_msg_and_die("can't swab %lu byte buffer",
+                                               (unsigned long)prev_read_size);
+                       prev_read_size = n;
+
+                       /*
+                        * If n is odd, last byte is not swapped:
                         *  echo -n "qwe" | dd conv=swab
                         * prints "wqe".
                         * The code does not handle correctly odd-sized reads
                         * in the *middle* of the input. FIXME.
                         */
-                       uint16_t *p16 = (void*) ibuf;
-                       uint16_t *end = (void*) (ibuf + (n & ~(ssize_t)1));
+                       p16 = (void*) ibuf;
+                       end = (void*) (ibuf + (n & ~(ssize_t)1));
                        while (p16 < end) {
                                *p16 = bswap_16(*p16);
                                p16++;