From 4b96679170c63be361d1b0fdeb81bb0ef207dbcb Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Fri, 7 Jul 2023 16:09:26 -0700 Subject: [PATCH] libsubcmd: Avoid SEGV/use-after-free when commands aren't excluded The array shortening may perform unnecessary array copies. Before commit 657a3efee43a ("lib subcmd: Avoid memory leak in exclude_cmds") this was benign, but afterwards this could lead to a SEGV. Fixes: 657a3efee43a29d1 ("lib subcmd: Avoid memory leak in exclude_cmds") Signed-off-by: Ian Rogers Acked-by: Namhyung Kim Cc: Chenyuan Mi Cc: Ian Rogers Link: https://lore.kernel.org/r/20230707230926.841086-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/lib/subcmd/help.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/tools/lib/subcmd/help.c b/tools/lib/subcmd/help.c index 67a8d6b740ea..adfbae27dc36 100644 --- a/tools/lib/subcmd/help.c +++ b/tools/lib/subcmd/help.c @@ -68,8 +68,13 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes) while (ci < cmds->cnt && ei < excludes->cnt) { cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name); if (cmp < 0) { - zfree(&cmds->names[cj]); - cmds->names[cj++] = cmds->names[ci++]; + if (ci == cj) { + ci++; + cj++; + } else { + zfree(&cmds->names[cj]); + cmds->names[cj++] = cmds->names[ci++]; + } } else if (cmp == 0) { ci++; ei++; @@ -77,10 +82,11 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes) ei++; } } - - while (ci < cmds->cnt) { - zfree(&cmds->names[cj]); - cmds->names[cj++] = cmds->names[ci++]; + if (ci != cj) { + while (ci < cmds->cnt) { + zfree(&cmds->names[cj]); + cmds->names[cj++] = cmds->names[ci++]; + } } for (ci = cj; ci < cmds->cnt; ci++) zfree(&cmds->names[ci]);