Subject: [PATCH] commit-graph: avoid leaking topo_levels slab in write_commit_graph()

From: "Andrzej Hunt via GitGitGadget" <[email-masked]>
Date: Fri, 19 Feb 2021 20:13:10 +0000

From: Andrzej Hunt <[email-masked]>

write_commit_graph initialises topo_levels using init_topo_level_slab(),
next it calls compute_topological_levels() which can cause the slab to
grow, we therefore need to clear the slab again using
clear_topo_level_slab() when we're done.

First introduced in 72a2bfcaf01860ce8dd6921490d903dc0ad59c89 - which
is currently only in master and not on maint.

LeakSanitizer output:

==1026==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 8 byte(s) in 1 object(s) allocated from:
    #0 0x498ae9 in realloc /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
    #1 0xafbed8 in xrealloc /src/git/wrapper.c:126:8
    #2 0x7966d1 in topo_level_slab_at_peek /src/git/commit-graph.c:71:1
    #3 0x7965e0 in topo_level_slab_at /src/git/commit-graph.c:71:1
    #4 0x78fbf5 in compute_topological_levels /src/git/commit-graph.c:1472:12
    #5 0x78c5c3 in write_commit_graph /src/git/commit-graph.c:2456:2
    #6 0x535c5f in graph_write /src/git/builtin/commit-graph.c:299:6
    #7 0x5350ca in cmd_commit_graph /src/git/builtin/commit-graph.c:337:11
    #8 0x4cddb1 in run_builtin /src/git/git.c:453:11
    #9 0x4cabe2 in handle_builtin /src/git/git.c:704:3
    #10 0x4cd084 in run_argv /src/git/git.c:771:4
    #11 0x4ca424 in cmd_main /src/git/git.c:902:19
    #12 0x707fb6 in main /src/git/common-main.c:52:11
    #13 0x7fee4249383f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)

Indirect leak of 524256 byte(s) in 1 object(s) allocated from:
    #0 0x498942 in calloc /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:154:3
    #1 0xafc088 in xcalloc /src/git/wrapper.c:140:8
    #2 0x796870 in topo_level_slab_at_peek /src/git/commit-graph.c:71:1
    #3 0x7965e0 in topo_level_slab_at /src/git/commit-graph.c:71:1
    #4 0x78fbf5 in compute_topological_levels /src/git/commit-graph.c:1472:12
    #5 0x78c5c3 in write_commit_graph /src/git/commit-graph.c:2456:2
    #6 0x535c5f in graph_write /src/git/builtin/commit-graph.c:299:6
    #7 0x5350ca in cmd_commit_graph /src/git/builtin/commit-graph.c:337:11
    #8 0x4cddb1 in run_builtin /src/git/git.c:453:11
    #9 0x4cabe2 in handle_builtin /src/git/git.c:704:3
    #10 0x4cd084 in run_argv /src/git/git.c:771:4
    #11 0x4ca424 in cmd_main /src/git/git.c:902:19
    #12 0x707fb6 in main /src/git/common-main.c:52:11
    #13 0x7fee4249383f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)

SUMMARY: AddressSanitizer: 524264 byte(s) leaked in 2 allocation(s).

Signed-off-by: Andrzej Hunt <[email-masked]>
---
    commit-graph: avoid leaking topo_levels slab in write_commit_graph()
    
    write_commit_graph initialises topo_levels using init_topo_level_slab(),
    next it calls compute_topological_levels() which can cause the slab to
    grow, we therefore need to clear the slab again using
    clear_topo_level_slab() when we're done.
    
    First introduced in 72a2bfcaf01860ce8dd6921490d903dc0ad59c89 - which is
    currently only in master and not on maint.
    
    LeakSanitizer output:
    
    ==1026==ERROR: LeakSanitizer: detected memory leaks
    
    Direct leak of 8 byte(s) in 1 object(s) allocated from: #0 0x498ae9 in
    realloc
    /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3 #1
    0xafbed8 in xrealloc /src/git/wrapper.c:126:8 #2 0x7966d1 in
    topo_level_slab_at_peek /src/git/commit-graph.c:71:1 #3 0x7965e0 in
    topo_level_slab_at /src/git/commit-graph.c:71:1 #4 0x78fbf5 in
    compute_topological_levels /src/git/commit-graph.c:1472:12 #5 0x78c5c3
    in write_commit_graph /src/git/commit-graph.c:2456:2 #6 0x535c5f in
    graph_write /src/git/builtin/commit-graph.c:299:6 #7 0x5350ca in
    cmd_commit_graph /src/git/builtin/commit-graph.c:337:11 #8 0x4cddb1 in
    run_builtin /src/git/git.c:453:11 #9 0x4cabe2 in handle_builtin
    /src/git/git.c:704:3 #10 0x4cd084 in run_argv /src/git/git.c:771:4 #11
    0x4ca424 in cmd_main /src/git/git.c:902:19 #12 0x707fb6 in main
    /src/git/common-main.c:52:11 #13 0x7fee4249383f in __libc_start_main
    (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)
    
    Indirect leak of 524256 byte(s) in 1 object(s) allocated from: #0
    0x498942 in calloc
    /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:154:3 #1
    0xafc088 in xcalloc /src/git/wrapper.c:140:8 #2 0x796870 in
    topo_level_slab_at_peek /src/git/commit-graph.c:71:1 #3 0x7965e0 in
    topo_level_slab_at /src/git/commit-graph.c:71:1 #4 0x78fbf5 in
    compute_topological_levels /src/git/commit-graph.c:1472:12 #5 0x78c5c3
    in write_commit_graph /src/git/commit-graph.c:2456:2 #6 0x535c5f in
    graph_write /src/git/builtin/commit-graph.c:299:6 #7 0x5350ca in
    cmd_commit_graph /src/git/builtin/commit-graph.c:337:11 #8 0x4cddb1 in
    run_builtin /src/git/git.c:453:11 #9 0x4cabe2 in handle_builtin
    /src/git/git.c:704:3 #10 0x4cd084 in run_argv /src/git/git.c:771:4 #11
    0x4ca424 in cmd_main /src/git/git.c:902:19 #12 0x707fb6 in main
    /src/git/common-main.c:52:11 #13 0x7fee4249383f in __libc_start_main
    (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)
    
    SUMMARY: AddressSanitizer: 524264 byte(s) leaked in 2 allocation(s).

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-881%2Fahunt%2Fcommit-graph-leak-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-881/ahunt/commit-graph-leak-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/881

 commit-graph.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/commit-graph.c b/commit-graph.c
index ed31843fa522..9529ec552139 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -2471,6 +2471,7 @@ int write_commit_graph(struct object_directory *odb,
 	free(ctx->graph_name);
 	free(ctx->commits.list);
 	oid_array_clear(&ctx->oids);
+	clear_topo_level_slab(&topo_levels);
 
 	if (ctx->commit_graph_filenames_after) {
 		for (i = 0; i < ctx->num_commit_graphs_after; i++) {

base-commit: 2283e0e9af55689215afa39c03beb2315ce18e83
-- 
gitgitgadget