On Tue, Dec 11, 2018 at 07:45:29AM +0100, Florian Westphal wrote: > The dst entry might already have a zero refcount, waiting on rcu list > to be free'd. Using dst_hold() transitions its reference count to 1, and > next dst release will try to free it again -- resulting in a double free: > > WARNING: CPU: 1 PID: 0 at include/net/dst.h:239 nf_xfrm_me_harder+0xe7/0x130 [nf_nat] > RIP: 0010:nf_xfrm_me_harder+0xe7/0x130 [nf_nat] > Code: 48 8b 5c 24 60 65 48 33 1c 25 28 00 00 00 75 53 48 83 c4 68 5b 5d 41 5c c3 85 c0 74 0d 8d 48 01 f0 0f b1 0a 74 86 85 c0 75 f3 <0f> 0b e9 7b ff ff ff 29 c6 31 d2 b9 20 00 48 00 4c 89 e7 e8 31 27 > Call Trace: > nf_nat_ipv4_out+0x78/0x90 [nf_nat_ipv4] > nf_hook_slow+0x36/0xd0 > ip_output+0x9f/0xd0 > ip_forward+0x328/0x440 > ip_rcv+0x8a/0xb0 > > Use dst_hold_safe instead and bail out if we cannot take a reference. Applied, thanks Florian.
