Author: cem
Date: Sat Jul 9 17:11:54 2016
New Revision: 302500
URL: https://svnweb.freebsd.org/changeset/base/302500
Log:
dd(1): Enable access to SIZE_T_MAX character devices
On machines where SIZE_T_MAX exceeds OFF_MAX (signed 64-bit), permit seeking
character devices to negative off_t values. This enables dd(1) to interact
with kernel KVA in /dev/kmem on amd64, for example.
Sponsored by: EMC / Isilon Storage Division
Modified:
head/bin/dd/args.c
head/bin/dd/position.c
Modified: head/bin/dd/args.c
==============================================================================
--- head/bin/dd/args.c Sat Jul 9 14:59:16 2016 (r302499)
+++ head/bin/dd/args.c Sat Jul 9 17:11:54 2016 (r302500)
@@ -167,14 +167,6 @@ jcl(char **argv)
errx(1, "cbs meaningless if not doing record
operations");
} else
cfunc = def;
-
- /*
- * Bail out if the calculation of a file offset would overflow.
- */
- if (in.offset > OFF_MAX / (ssize_t)in.dbsz ||
- out.offset > OFF_MAX / (ssize_t)out.dbsz)
- errx(1, "seek offsets cannot be larger than %jd",
- (intmax_t)OFF_MAX);
}
static int
Modified: head/bin/dd/position.c
==============================================================================
--- head/bin/dd/position.c Sat Jul 9 14:59:16 2016 (r302499)
+++ head/bin/dd/position.c Sat Jul 9 17:11:54 2016 (r302500)
@@ -45,12 +45,41 @@ __FBSDID("$FreeBSD$");
#include <err.h>
#include <errno.h>
#include <inttypes.h>
+#include <limits.h>
#include <signal.h>
#include <unistd.h>
#include "dd.h"
#include "extern.h"
+static off_t
+seek_offset(IO *io)
+{
+ off_t n;
+ size_t sz;
+
+ n = io->offset;
+ sz = io->dbsz;
+
+ _Static_assert(sizeof(io->offset) == sizeof(int64_t), "64-bit off_t");
+
+ /*
+ * If the lseek offset will be negative, verify that this is a special
+ * device file. Some such files (e.g. /dev/kmem) permit "negative"
+ * offsets.
+ *
+ * Bail out if the calculation of a file offset would overflow.
+ */
+ if ((io->flags & ISCHR) == 0 && n > OFF_MAX / (ssize_t)sz)
+ errx(1, "seek offsets cannot be larger than %jd",
+ (intmax_t)OFF_MAX);
+ else if ((io->flags & ISCHR) != 0 && (uint64_t)n > UINT64_MAX / sz)
+ errx(1, "seek offsets cannot be larger than %ju",
+ (uintmax_t)UINT64_MAX);
+
+ return ((off_t)( (uint64_t)n * sz ));
+}
+
/*
* Position input/output data streams before starting the copy. Device type
* dependent. Seekable devices use lseek, and the rest position by reading.
@@ -68,7 +97,7 @@ pos_in(void)
/* If known to be seekable, try to seek on it. */
if (in.flags & ISSEEK) {
errno = 0;
- if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1 &&
+ if (lseek(in.fd, seek_offset(&in), SEEK_CUR) == -1 &&
errno != 0)
err(1, "%s", in.name);
return;
@@ -136,7 +165,7 @@ pos_out(void)
*/
if (out.flags & (ISSEEK | ISPIPE)) {
errno = 0;
- if (lseek(out.fd, out.offset * out.dbsz, SEEK_CUR) == -1 &&
+ if (lseek(out.fd, seek_offset(&out), SEEK_CUR) == -1 &&
errno != 0)
err(1, "%s", out.name);
return;
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