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authorMichael Ellerman <mpe@ellerman.id.au>2017-07-14 14:49:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-14 15:05:13 -0700
commitffba19ccae8d98beb0a17345a0b1ee9e415b23b8 (patch)
tree296a447d459113fb7fb12c25c238409c542b9485
parentmm: fix overflow check in expand_upwards() (diff)
downloadlinux-dev-ffba19ccae8d98beb0a17345a0b1ee9e415b23b8.tar.xz
linux-dev-ffba19ccae8d98beb0a17345a0b1ee9e415b23b8.zip
lib/atomic64_test.c: add a test that atomic64_inc_not_zero() returns an int
atomic64_inc_not_zero() returns a "truth value" which in C is traditionally an int. That means callers are likely to expect the result will fit in an int. If an implementation returns a "true" value which does not fit in an int, then there's a possibility that callers will truncate it when they store it in an int. In fact this happened in practice, see commit 966d2b04e070 ("percpu-refcount: fix reference leak during percpu-atomic transition"). So add a test that the result fits in an int, even when the input doesn't. This catches the case where an implementation just passes the non-zero input value out as the result. Link: http://lkml.kernel.org/r/1499775133-1231-1-git-send-email-mpe@ellerman.id.au Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Douglas Miller <dougmill@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/atomic64_test.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c
index fd70c0e0e673..62ab629f51ca 100644
--- a/lib/atomic64_test.c
+++ b/lib/atomic64_test.c
@@ -153,8 +153,10 @@ static __init void test_atomic64(void)
long long v0 = 0xaaa31337c001d00dLL;
long long v1 = 0xdeadbeefdeafcafeLL;
long long v2 = 0xfaceabadf00df001LL;
+ long long v3 = 0x8000000000000000LL;
long long onestwos = 0x1111111122222222LL;
long long one = 1LL;
+ int r_int;
atomic64_t v = ATOMIC64_INIT(v0);
long long r = v0;
@@ -240,6 +242,11 @@ static __init void test_atomic64(void)
BUG_ON(!atomic64_inc_not_zero(&v));
r += one;
BUG_ON(v.counter != r);
+
+ /* Confirm the return value fits in an int, even if the value doesn't */
+ INIT(v3);
+ r_int = atomic64_inc_not_zero(&v);
+ BUG_ON(!r_int);
}
static __init int test_atomics_init(void)