[PATCH 0/2] various safety fixes from the Perl side

[PATCH 0/2] various safety fixes from the Perl side

[Eric Wong]

It's unlikely any of these affect applications today, but
Ractor use may increase in the future; and maybe some
maniac will use giant __FILE__ replacements via eval.

Eric Wong (2):
  Ractor compatibility
  paranoid safety fix to clamp pathnames to PATH_MAX

 ext/mwrap/mwrap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

[PATCH 1/2] Ractor compatibility

[Eric Wong]

We can no longer depend on having GVL/GIL when we have a Ruby
execution context, so so make `kbuf' thread-specific to avoid
data corruption.

This was ported from the Perl5 version, since Perl5 has had
MVM/Ractor-like abilities with native threads for decades,
despite the Perl5 ecosystem largely avoids and discourages
threads.
---
 ext/mwrap/mwrap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
index 1d6baec..90f560e 100644
--- a/ext/mwrap/mwrap.c
+++ b/ext/mwrap/mwrap.c
@@ -308,7 +308,9 @@ struct alloc_hdr {
 	size_t size;
 };
 
-static char kbuf[PATH_MAX + INT2STR_MAX + sizeof(struct alloc_hdr) + 2];
+static MWRAP_TSD char kbuf[
+	PATH_MAX + INT2STR_MAX + sizeof(struct alloc_hdr) + 2
+];
 
 static struct alloc_hdr *ptr2hdr(void *p)
 {

[PATCH 2/2] paranoid safety fix to clamp pathnames to PATH_MAX

[Eric Wong]

While I doubt Ruby (nor Perl) would store pathnames longer than
PATH_MAX by default, it's possible `eval' users to specify
whatever path (and line number) they wish to use.

Likely was the case with `# line $FILE' directives in Perl5
which prompted this clamping.
---
 ext/mwrap/mwrap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
index 90f560e..08761d6 100644
--- a/ext/mwrap/mwrap.c
+++ b/ext/mwrap/mwrap.c
@@ -470,6 +470,8 @@ static struct src_loc *update_stats_rcu_lock(size_t size, uintptr_t caller)
 
 		/* avoid vsnprintf or anything which could call malloc here: */
 		len = strlen(ptr);
+		if (len > PATH_MAX)
+			len = PATH_MAX;
 		k = (void *)kbuf;
 		k->total = size;
 		dst = mempcpy(k->k, ptr, len);