[PATCH] lib: Fix bug in int_sqrt() for 64 bit longs

The implementation of int_sqrt() assumes that longs have 32 bits.  On
systems that have 64 bit longs this will result in gross errors when the
argument to the function is greater than 2^32 - 1 on such systems.  I doubt
whether any such use is currently made of int_sqrt() but the attached patch
fixes the problem anyway.

Signed-off-by: Peter Williams <[email protected]>
Cc: Dave Jones <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c
index a5d2cdc5684cfdf0d2834692c3abc6024da515de..fd355a99327cdeab8333781991ea3ecd59997ca4 100644 (file)
--- a/lib/int_sqrt.c
+++ b/lib/int_sqrt.c
@@ -15,7 +15,7 @@ unsigned long int_sqrt(unsigned long x)
        op = x;
        res = 0;
 
-       one = 1 << 30;
+       one = 1UL << (BITS_PER_LONG - 2);
        while (one > op)
                one >>= 2;