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Origin: http://repo.or.cz/w/libtar.git/commitdiff/e4c1f2974258d6a325622cfd712873d49b5e7a73

From: Chris Frey <cdfrey@foursquare.net>

Date: Thu, 24 Oct 2013 18:52:44 -0400

Subject: [PATCH] Change th_get_size() macro to return unsigned int

On systems where size_t is larger than an int (and larger than

unsigned int), then in various places in the library, where

stuff like this happens:

        size_t sz = th_get_size(t);

then the int value returned from th_get_size() is sign extended to

some unwieldy amount.

On 64bit systems, this can yield extremely large values.

By fixing this problem in the header, and only for th_get_size(),

we avoid breaking the API of the function call oct_to_int()

(which arguably should return an unsigned int, since the sscanf()

it uses expects to yield an unsigned int).  We also fix the library,

which uses th_get_size() internally to assign sizes to size_t.

The drawback is that not all client code that uses th_get_size()

will be fixed, until they recompile, but they will automatically

take advantage of the bugs fixed *inside* the library.

The remaining th_get_*() functions operate on modes and CRC values

and the like, and should be fine, remaining as ints.

Thanks very much to Magnus Holmgren for catching this behaviour.

https://lists.feep.net:8080/pipermail/libtar/2013-October/000365.html

---

 lib/libtar.h | 6 +++++-

 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/libtar.h b/lib/libtar.h

index 2fefee0..13bb82d 100644

--- a/lib/libtar.h

+++ b/lib/libtar.h

@@ -185,7 +185,11 @@ int th_write(TAR *t);

 /* decode tar header info */

 #define th_get_crc(t) oct_to_int((t)->th_buf.chksum)

-#define th_get_size(t) oct_to_int((t)->th_buf.size)

+/* We cast from int (what oct_to_int() returns) to

+   unsigned int, to avoid unwieldy sign extensions

+   from occurring on systems where size_t is bigger than int,

+   since th_get_size() is often stored into a size_t. */

+#define th_get_size(t) ((unsigned int)oct_to_int((t)->th_buf.size))

 #define th_get_mtime(t) oct_to_int((t)->th_buf.mtime)

 #define th_get_devmajor(t) oct_to_int((t)->th_buf.devmajor)

 #define th_get_devminor(t) oct_to_int((t)->th_buf.devminor)