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authorEric Dumazet <edumazet@google.com>2016-09-20 18:06:17 -0700
committerDavid S. Miller <davem@davemloft.net>2016-09-22 02:41:17 -0400
commitadb03115f4590baa280ddc440a8eff08a6be0cb7 (patch)
tree66b36cd6c485ea989a634ab49cc937dc5451ba3d /net
parentfba1296624bf95fc07057da1e26beee8a733180c (diff)
downloadlinux-stericsson-adb03115f4590baa280ddc440a8eff08a6be0cb7.tar.gz
net: get rid of an signed integer overflow in ip_idents_reserve()
Jiri Pirko reported an UBSAN warning happening in ip_idents_reserve() [] UBSAN: Undefined behaviour in ./arch/x86/include/asm/atomic.h:156:11 [] signed integer overflow: [] -2117905507 + -695755206 cannot be represented in type 'int' Since we do not have uatomic_add_return() yet, use atomic_cmpxchg() so that the arithmetics can be done using unsigned int. Fixes: 04ca6973f7c1 ("ip: make IP identifiers less predictable") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jiri Pirko <jiri@resnulli.us> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/route.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a1f2830d8110..b5b47a26d4ec 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -476,12 +476,18 @@ u32 ip_idents_reserve(u32 hash, int segs)
atomic_t *p_id = ip_idents + hash % IP_IDENTS_SZ;
u32 old = ACCESS_ONCE(*p_tstamp);
u32 now = (u32)jiffies;
- u32 delta = 0;
+ u32 new, delta = 0;
if (old != now && cmpxchg(p_tstamp, old, now) == old)
delta = prandom_u32_max(now - old);
- return atomic_add_return(segs + delta, p_id) - segs;
+ /* Do not use atomic_add_return() as it makes UBSAN unhappy */
+ do {
+ old = (u32)atomic_read(p_id);
+ new = old + delta + segs;
+ } while (atomic_cmpxchg(p_id, old, new) != old);
+
+ return new - segs;
}
EXPORT_SYMBOL(ip_idents_reserve);