From 7d6b4a820f3adf9c41fcee2a1350ec0b71f079c1 Mon Sep 17 00:00:00 2001 From: Volker Lendecke Date: Fri, 30 Sep 2022 17:02:41 +0200 Subject: [PATCH] ctdb: Fix a use-after-free in run_proc If you happen to talloc_free(run_ctx) before all the tevent_req's hanging off it, you run into the following: ==495196== Invalid read of size 8 ==495196== at 0x10D757: run_proc_state_destructor (run_proc.c:413) ==495196== by 0x488F736: _tc_free_internal (talloc.c:1158) ==495196== by 0x488FBDD: _talloc_free_internal (talloc.c:1248) ==495196== by 0x4890F41: _talloc_free (talloc.c:1792) ==495196== by 0x48538B1: tevent_req_received (tevent_req.c:293) ==495196== by 0x4853429: tevent_req_destructor (tevent_req.c:129) ==495196== by 0x488F736: _tc_free_internal (talloc.c:1158) ==495196== by 0x4890AF6: _tc_free_children_internal (talloc.c:1669) ==495196== by 0x488F967: _tc_free_internal (talloc.c:1184) ==495196== by 0x488FBDD: _talloc_free_internal (talloc.c:1248) ==495196== by 0x4890F41: _talloc_free (talloc.c:1792) ==495196== by 0x10DE62: main (run_proc_test.c:86) ==495196== Address 0x55b77f8 is 152 bytes inside a block of size 160 free'd ==495196== at 0x48399AB: free (vg_replace_malloc.c:538) ==495196== by 0x488FB25: _tc_free_internal (talloc.c:1222) ==495196== by 0x488FBDD: _talloc_free_internal (talloc.c:1248) ==495196== by 0x4890F41: _talloc_free (talloc.c:1792) ==495196== by 0x10D315: run_proc_context_destructor (run_proc.c:329) ==495196== by 0x488F736: _tc_free_internal (talloc.c:1158) ==495196== by 0x488FBDD: _talloc_free_internal (talloc.c:1248) ==495196== by 0x4890F41: _talloc_free (talloc.c:1792) ==495196== by 0x10DE62: main (run_proc_test.c:86) ==495196== Block was alloc'd at ==495196== at 0x483877F: malloc (vg_replace_malloc.c:307) ==495196== by 0x488EAD9: __talloc_with_prefix (talloc.c:783) ==495196== by 0x488EC73: __talloc (talloc.c:825) ==495196== by 0x488F0FC: _talloc_named_const (talloc.c:982) ==495196== by 0x48925B1: _talloc_zero (talloc.c:2421) ==495196== by 0x10C8F2: proc_new (run_proc.c:61) ==495196== by 0x10D4C9: run_proc_send (run_proc.c:381) ==495196== by 0x10DDF6: main (run_proc_test.c:79) This happens because run_proc_context_destructor() directly does a talloc_free() on the struct proc_context's and not the enclosing tevent_req's. run_proc_kill() makes sure that we don't follow proc->req, but it forgets the "state->proc", which is free()'ed, but later dereferenced in run_proc_state_destructor(). This is an attempt at a quick fix, I believe we should convert run_proc_context->plist into an array of tevent_req's, so that we can properly TALLOC_FREE() according to the "natural" hierarchy and not just pull an arbitrary thread out of that heap. BUG: https://bugzilla.samba.org/show_bug.cgi?id=15269 Signed-off-by: Volker Lendecke Reviewed-by: Martin Schwenke Autobuild-User(master): Volker Lendecke Autobuild-Date(master): Thu Oct 6 15:10:20 UTC 2022 on sn-devel-184 (cherry picked from commit 688be0177b04d04709813a02ae6da1e983ac25dd) --- ctdb/common/run_proc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/ctdb/common/run_proc.c b/ctdb/common/run_proc.c index d55af6c3a1e..84bc343ba1f 100644 --- a/ctdb/common/run_proc.c +++ b/ctdb/common/run_proc.c @@ -408,10 +408,10 @@ struct tevent_req *run_proc_send(TALLOC_CTX *mem_ctx, static int run_proc_state_destructor(struct run_proc_state *state) { /* Do not get rid of the child process if timeout has occurred */ - if (state->proc->req != NULL) { + if ((state->proc != NULL) && (state->proc->req != NULL)) { state->proc->req = NULL; DLIST_REMOVE(state->run_ctx->plist, state->proc); - talloc_free(state->proc); + TALLOC_FREE(state->proc); } return 0; @@ -439,6 +439,7 @@ static void run_proc_kill(struct tevent_req *req) req, struct run_proc_state); state->proc->req = NULL; + state->proc = NULL; state->result.sig = SIGKILL; -- 2.34.1