linux/kernel.h: fix overflow for DIV_ROUND_UP_ULL

DIV_ROUND_UP_ULL adds the two arguments and then invokes DIV_ROUND_DOWN_ULL. But on a 32bit system the addition of two 32 bit values can overflow. DIV_ROUND_DOWN_ULL does it correctly and stashes the addition into a unsigned long long so cast the result to unsigned long long here to avoid the overflow condition. [[email protected]: DIV_ROUND_UP_ULL must be an rval] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Vinod Koul <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: Bjorn Andersson <[email protected]> Cc: Randy Dunlap <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
modi0012 · Jun 29, 2019 · 8f9fab4 · 8f9fab4
1 parent 1a5f439
commit 8f9fab4
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
@@ -93,7 +93,8 @@
 #define DIV_ROUND_DOWN_ULL(ll, d) \
 	({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; })
 
-#define DIV_ROUND_UP_ULL(ll, d)		DIV_ROUND_DOWN_ULL((ll) + (d) - 1, (d))
+#define DIV_ROUND_UP_ULL(ll, d) \
+	DIV_ROUND_DOWN_ULL((unsigned long long)(ll) + (d) - 1, (d))
 
 #if BITS_PER_LONG == 32
 # define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)