Commit d85ef0d5 authored by Nick Mathewson's avatar Nick Mathewson 🦀
Browse files

Merge branch 'ticket40382_045' into maint-0.4.5

parents 7c86f343 f5acfe67
Pipeline #5940 passed with stage
in 19 minutes and 36 seconds
o Minor features (compatibility, Linux seccomp sandbox):
- Add a workaround to enable the Linux sandbox to work correctly
on systems running Glibc 2.33. These versions have started
using the fstatat() system call, which previously our sandbox did not
Closes ticket 40382; see the ticket for a discussion of tradeoffs.
......@@ -1608,6 +1608,28 @@ add_noparam_filter(scmp_filter_ctx ctx)
if (is_libc_at_least(2, 33)) {
#ifdef __NR_newfstatat
// Libc 2.33 uses this syscall to implement both fstat() and stat().
// The trouble is that to implement fstat(fd, &st), it calls:
// newfstatat(fs, "", &st, AT_EMPTY_PATH)
// We can't detect this usage in particular, because "" is a pointer
// we don't control. And we can't just look for AT_EMPTY_PATH, since
// AT_EMPTY_PATH only has effect when the path string is empty.
// So our only solution seems to be allowing all fstatat calls, which
// means that an attacker can stat() anything on the filesystem. That's
// not a great solution, but I can't find a better one.
rc = seccomp_rule_add_0(ctx, SCMP_ACT_ALLOW, SCMP_SYS(newfstatat));
if (rc != 0) {
log_err(LD_BUG,"(Sandbox) failed to add newfstatat() syscall; "
"received libseccomp error %d", rc);
return rc;
return 0;
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