From a08eabc6e5a3e0a9c7a15ca15ff7d450ecb6db88 Mon Sep 17 00:00:00 2001 From: Jan Engelhardt Date: Tue, 12 Oct 2021 17:32:43 +0200 Subject: [PATCH] io: fix a use-after-free in conjunction with HX_realpath HX_readlink(&x, ...) forgot to set x to nullptr upon error, which trips up subsequent calls to HX_readlink with the very same x. Fixes: v3.26-1-g97f4be2 --- src/io.c | 8 ++++++-- src/tc-realpath.c | 10 ++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/src/io.c b/src/io.c index 95d6fd6..14078fc 100644 --- a/src/io.c +++ b/src/io.c @@ -316,8 +316,10 @@ EXPORT_SYMBOL int HX_readlink(hxmc_t **target, const char *path) ssize_t ret = readlink(path, *target, linkbuf_size); if (ret < 0) { int saved_errno = errno; - if (allocate) + if (allocate) { HXmc_free(*target); + *target = nullptr; + } return -(errno = saved_errno); } if (static_cast(size_t, ret) < linkbuf_size) { @@ -327,8 +329,10 @@ EXPORT_SYMBOL int HX_readlink(hxmc_t **target, const char *path) linkbuf_size *= 2; if (HXmc_setlen(target, linkbuf_size) == NULL) { int saved_errno = errno; - if (allocate) + if (allocate) { HXmc_free(*target); + *target = nullptr; + } return -(errno = saved_errno); } } diff --git a/src/tc-realpath.c b/src/tc-realpath.c index 5dd9aa2..c2ef15a 100644 --- a/src/tc-realpath.c +++ b/src/tc-realpath.c @@ -11,6 +11,7 @@ #include #include #include +#include static unsigned int rp_flags; static unsigned int rp_absolute; @@ -42,6 +43,14 @@ static bool rp_get_options(int *argc, const char ***argv) return true; } +static void t_1(void) +{ + hxmc_t *tmp = HXmc_strinit(""); + /* two components, so that HX_readlink gets called twice */ + HX_realpath(&tmp, "/dev/tty", HX_REALPATH_DEFAULT); + HXmc_free(tmp); +} + int main(int argc, const char **argv) { hxmc_t *res; @@ -49,6 +58,7 @@ int main(int argc, const char **argv) if (!rp_get_options(&argc, &argv)) return EXIT_FAILURE; + t_1(); res = NULL; while (--argc > 0) { -- 2.33.0