diff options
| author | Eric Dumazet <edumazet@google.com> | 2016-09-20 18:06:17 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-09-22 02:41:17 -0400 |
| commit | adb03115f4590baa280ddc440a8eff08a6be0cb7 (patch) | |
| tree | 66b36cd6c485ea989a634ab49cc937dc5451ba3d /net/ipv4 | |
| parent | fba1296624bf95fc07057da1e26beee8a733180c (diff) | |
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/ipv4')
| -rw-r--r-- | net/ipv4/route.c | 10 |
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); |