| Message ID | 138a5ded35a43d3aeaa5058ba316a45b7b50b9ef.1724656120.git.ps@pks.im (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Memory leak fixes (pt.6) | expand |
Patrick Steinhardt <ps@pks.im> writes: > When retrieving the push cert nonce from the server, we first store the > constant returned by `server_feature_value()` and then, if the nonce is > valid, we duplicate the nonce memory to extend its lifetime. We never > free the latter and thus cause a memory leak. "to extend its lifetime" -> "to a NUL-terminated string, so that we can pass it to generate_push_cert()". What is going on in this code path is this. The other side may send a nonce in the server capability. We die if that nonce is bogus. Otherwise we make a xmemdupz() copy because we need to pass the nonce to generate_push_cert() that expects nonce to be a NUL terminated string (the original server capability is a long concatenation of capabilities and we learn the <ptr, len> for the nonce). The function cryptographically signs the ref update request we have, together with the nonce we got from the server, so that the other side can validate that it is signed by us, and the nonce serves as a protection against replay attacks. > diff --git a/send-pack.c b/send-pack.c > index b224ef9fc5e..c37f6ab3c07 100644 > --- a/send-pack.c > +++ b/send-pack.c > @@ -501,7 +501,7 @@ int send_pack(struct send_pack_args *args, > unsigned cmds_sent = 0; > int ret; > struct async demux; > - const char *push_cert_nonce = NULL; > + char *push_cert_nonce = NULL; > struct packet_reader reader; > int use_bitmaps; This is a change necessary to avoid having to cast the parameter to free(). > @@ -550,10 +550,11 @@ int send_pack(struct send_pack_args *args, > > if (args->push_cert != SEND_PACK_PUSH_CERT_NEVER) { > size_t len; > - push_cert_nonce = server_feature_value("push-cert", &len); > - if (push_cert_nonce) { > - reject_invalid_nonce(push_cert_nonce, len); > - push_cert_nonce = xmemdupz(push_cert_nonce, len); > + const char *nonce = server_feature_value("push-cert", &len); > + > + if (nonce) { > + reject_invalid_nonce(nonce, len); > + push_cert_nonce = xmemdupz(nonce, len); And this hunk become needed because push_cert_nonce cannot receive the return value from server_feature_value() without stripping constness. > } else if (args->push_cert == SEND_PACK_PUSH_CERT_ALWAYS) { > die(_("the receiving end does not support --signed push")); > } else if (args->push_cert == SEND_PACK_PUSH_CERT_IF_ASKED) { > @@ -771,5 +772,6 @@ int send_pack(struct send_pack_args *args, > oid_array_clear(&commons); > strbuf_release(&req_buf); > strbuf_release(&cap_buf); > + free(push_cert_nonce); And this is my fault to forget freeing. Thanks for spotting and fixing. > return ret; > }
diff --git a/send-pack.c b/send-pack.c index b224ef9fc5e..c37f6ab3c07 100644 --- a/send-pack.c +++ b/send-pack.c @@ -501,7 +501,7 @@ int send_pack(struct send_pack_args *args, unsigned cmds_sent = 0; int ret; struct async demux; - const char *push_cert_nonce = NULL; + char *push_cert_nonce = NULL; struct packet_reader reader; int use_bitmaps; @@ -550,10 +550,11 @@ int send_pack(struct send_pack_args *args, if (args->push_cert != SEND_PACK_PUSH_CERT_NEVER) { size_t len; - push_cert_nonce = server_feature_value("push-cert", &len); - if (push_cert_nonce) { - reject_invalid_nonce(push_cert_nonce, len); - push_cert_nonce = xmemdupz(push_cert_nonce, len); + const char *nonce = server_feature_value("push-cert", &len); + + if (nonce) { + reject_invalid_nonce(nonce, len); + push_cert_nonce = xmemdupz(nonce, len); } else if (args->push_cert == SEND_PACK_PUSH_CERT_ALWAYS) { die(_("the receiving end does not support --signed push")); } else if (args->push_cert == SEND_PACK_PUSH_CERT_IF_ASKED) { @@ -771,5 +772,6 @@ int send_pack(struct send_pack_args *args, oid_array_clear(&commons); strbuf_release(&req_buf); strbuf_release(&cap_buf); + free(push_cert_nonce); return ret; }
When retrieving the push cert nonce from the server, we first store the constant returned by `server_feature_value()` and then, if the nonce is valid, we duplicate the nonce memory to extend its lifetime. We never free the latter and thus cause a memory leak. Fix this by storing the limited-lifetime nonce into a scope-local variable such that the long-lived, allocated nonce can be easily freed without having to cast away its constness. This leak was exposed by t5534, but fixing it is not sufficient to make the whole test suite leak free. Signed-off-by: Patrick Steinhardt <ps@pks.im> --- send-pack.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)