Commit 4d2176df2985 ("handshake: Allow event handler to free handshake") introduced a re-entrancy guard so that handshake_state objects that are destroyed as a result of the event do not cause a crash. It rightly used a temporary object to store the passed in handshake. Unfortunately this caused variable shadowing which resulted in crashes fixed by commit d22b174a7318 ("handshake: use _hs directly in handshake_event"). However, since the temporary was no longer used, this fix itself caused a crash: #0 0x00005555f0ba8b3d in eapol_handle_ptk_1_of_4 (sm=sm@entry=0x5555f2b4a920, ek=0x5555f2b62588, ek@entry=0x16, unencrypted=unencrypted@entry=false) at src/eapol.c:1236 1236 handshake_event(sm->handshake, (gdb) bt #0 0x00005555f0ba8b3d in eapol_handle_ptk_1_of_4 (sm=sm@entry=0x5555f2b4a920, ek=0x5555f2b62588, ek@entry=0x16, unencrypted=unencrypted@entry=false) at src/eapol.c:1236 #1 0x00005555f0bab118 in eapol_key_handle (unencrypted=<optimized out>, frame=<optimized out>, sm=0x5555f2b4a920) at src/eapol.c:2343 #2 eapol_rx_packet (proto=<optimized out>, from=<optimized out>, frame=<optimized out>, unencrypted=<optimized out>, user_data=0x5555f2b4a920) at src/eapol.c:2665 #3 0x00005555f0bac497 in __eapol_rx_packet (ifindex=62, src=src@entry=0x5555f2b62574 "x\212 J\207\267", proto=proto@entry=34958, frame=frame@entry=0x5555f2b62588 "\002\003", len=len@entry=121, noencrypt=noencrypt@entry=false) at src/eapol.c:3017 #4 0x00005555f0b8c617 in netdev_control_port_frame_event (netdev=0x5555f2b64450, msg=0x5555f2b62588) at src/netdev.c:5574 #5 netdev_unicast_notify (msg=msg@entry=0x5555f2b619a0, user_data=<optimized out>) at src/netdev.c:5613 #6 0x00007f60084c9a51 in dispatch_unicast_watches (msg=0x5555f2b619a0, id=<optimized out>, genl=0x5555f2b3fc80) at ell/genl.c:954 #7 process_unicast (nlmsg=0x7fff61abeac0, genl=0x5555f2b3fc80) at ell/genl.c:973 #8 received_data (io=<optimized out>, user_data=0x5555f2b3fc80) at ell/genl.c:1098 #9 0x00007f60084c61bd in io_callback (fd=<optimized out>, events=1, user_data=0x5555f2b3fd20) at ell/io.c:120 #10 0x00007f60084c536d in l_main_iterate (timeout=<optimized out>) at ell/main.c:478 #11 0x00007f60084c543e in l_main_run () at ell/main.c:525 #12 l_main_run () at ell/main.c:507 #13 0x00007f60084c5670 in l_main_run_with_signal (callback=callback@entry=0x5555f0b89150 <signal_handler>, user_data=user_data@entry=0x0) at ell/main.c:647 #14 0x00005555f0b886a4 in main (argc=<optimized out>, argv=<optimized out>) at src/main.c:532 This happens when the driver does not support rekeying, which causes iwd to attempt a disconnect and re-connect. The disconnect action is taken during the event callback and destroys the underlying eapol state machine. Since a temporary isn't used, attempting to dereference sm->handshake results in a crash. Fix this by introducing a UNIQUE_ID macro which should prevent shadowing and using a temporary variable as originally intended. Fixes: d22b174a7318 ("handshake: use _hs directly in handshake_event") Fixes: 4d2176df2985 ("handshake: Allow event handler to free handshake") Reported-By: Toke Høiland-Jørgensen <toke(a)toke.dk&gt; --- src/handshake.h | 38 +++++++++++++++++++++----------------- src/util.h | 4 ++++ 2 files changed, 25 insertions(+), 17 deletions(-) diff --git a/src/handshake.h b/src/handshake.h index 7136087a1a4a..7f597b06078b 100644 --- a/src/handshake.h +++ b/src/handshake.h @@ -164,23 +164,27 @@ struct handshake_state { handshake_event_func_t event_func; }; -#define handshake_event(_hs, event, ...) \ - (__extension__ ({ \ - bool freed = false; \ - \ - if ((_hs)->event_func && !(_hs)->in_event) { \ - (_hs)->in_event = true; \ - (_hs)->event_func((_hs), event, (_hs)->user_data, \ - ##__VA_ARGS__); \ - \ - if (!(_hs)->in_event) { \ - handshake_state_free((_hs)); \ - freed = true; \ - } else \ - (_hs)->in_event = false; \ - } \ - freed; \ - })) +#define HSID(x) UNIQUE_ID(handshake_, x) + +#define handshake_event(_hs, event, ...) \ + ({ \ + bool HSID(freed) = false; \ + typeof(_hs) HSID(hs) = (_hs); \ + \ + if (HSID(hs)->event_func && !HSID(hs)->in_event) { \ + HSID(hs)->in_event = true; \ + HSID(hs)->event_func(HSID(hs), (event), \ + HSID(hs)->user_data, \ + ##__VA_ARGS__); \ + \ + if (!HSID(hs)->in_event) { \ + handshake_state_free(HSID(hs)); \ + HSID(freed) = true; \ + } else \ + HSID(hs)->in_event = false; \ + } \ + HSID(freed); \ + }) void handshake_state_free(struct handshake_state *s); diff --git a/src/util.h b/src/util.h index b55a7ea7cd6b..75c29039b04a 100644 --- a/src/util.h +++ b/src/util.h @@ -26,6 +26,10 @@ #include <stdint.h> #include <unistd.h> +#define ___PASTE(a, b) a ## b +#define __PASTE(a, b) ___PASTE(a, b) +#define UNIQUE_ID(x, id) __PASTE(__unique_prefix_, __PASTE(x, id)) + #define align_len(len, boundary) (((len)+(boundary)-1) & ~((boundary)-1)) #define MAC "%02x:%02x:%02x:%02x:%02x:%02x" -- 2.32.0