[tor-commits] [tor/release-0.3.4] Fix crash when calling openat with sandbox enabled #25440

[nickm at torproject.org]

commit a350f216b30c5841b8eb0303c9c3fd32a2b2245b
Author: Daniel Pinto <danielpinto52 at gmail.com>
Date:   Tue Apr 17 01:31:49 2018 +0100

    Fix crash when calling openat with sandbox enabled #25440
    
    The seccomp rule for the openat syscall checks for the AT_FDCWD
    constant. Because this constant is usually a negative value, a
    cast to unsigned int is necessary to make sure it does not get
    converted to uint64_t used by seccomp.
    
    More info on:
    https://github.com/seccomp/libseccomp/issues/69#issuecomment-273805980
---
 src/common/sandbox.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/sandbox.c b/src/common/sandbox.c
index 3d27ea66b..0a972d496 100644
--- a/src/common/sandbox.c
+++ b/src/common/sandbox.c
@@ -469,7 +469,7 @@ allow_file_open(scmp_filter_ctx ctx, int use_openat, const char *file)
 {
   if (use_openat) {
     return seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat),
-                              SCMP_CMP_STR(0, SCMP_CMP_EQ, AT_FDCWD),
+                              SCMP_CMP(0, SCMP_CMP_EQ, (unsigned int)AT_FDCWD),
                               SCMP_CMP_STR(1, SCMP_CMP_EQ, file));
   } else {
     return seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open),