# [PATCH 2/2] clone.c: don't leak memory in cmd_clone 6 messages from 2014-08-10 to 2014-08-10. Participants: Stefan Beller, Jeff King, Junio C Hamano. Thread: https://gitlist.dev/t/37321 ## Stefan Beller, 2014-08-10 13:57 Subject: [PATCH 1/2] remote.c: don't leak the base branch name in format_tracking_info Message-ID: <1407679076-20300-1-git-send-email-stefanbeller@gmail.com> URL: https://gitlist.dev/e/1407679076-20300-1-git-send-email-stefanbeller%40gmail.com ``` Found by scan.coverity.com (Id: 1127809) Signed-off-by: Stefan Beller --- remote.c | 1 + 1 file changed, 1 insertion(+) diff --git a/remote.c b/remote.c index 3d6c86a..2c1458f 100644 --- a/remote.c +++ b/remote.c @@ -1983,6 +1983,7 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb) strbuf_addf(sb, _(" (use \"git pull\" to merge the remote branch into yours)\n")); } + free(base); return 1; } -- 2.1.0.rc2 ``` ## Stefan Beller, 2014-08-10 13:57 Subject: [PATCH 2/2] clone.c: don't leak memory in cmd_clone Message-ID: <1407679076-20300-2-git-send-email-stefanbeller@gmail.com> URL: https://gitlist.dev/e/1407679076-20300-2-git-send-email-stefanbeller%40gmail.com In-Reply-To: <1407679076-20300-1-git-send-email-stefanbeller@gmail.com> ``` Free the refspec. Found by scan.coverity.com (Id: 1127806) Signed-off-by: Stefan Beller --- builtin/clone.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/builtin/clone.c b/builtin/clone.c index bbd169c..dd4092b 100644 --- a/builtin/clone.c +++ b/builtin/clone.c @@ -1004,5 +1004,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix) strbuf_release(&key); strbuf_release(&value); junk_mode = JUNK_LEAVE_ALL; + + free(refspec); return err; } -- 2.1.0.rc2 ``` ## Stefan Beller, 2014-08-10 15:14 Subject: Re: [PATCH 1/2] remote.c: don't leak the base branch name in format_tracking_info Message-ID: <53E78C59.2010704@gmail.com> URL: https://gitlist.dev/e/53E78C59.2010704%40gmail.com In-Reply-To: <1407679076-20300-1-git-send-email-stefanbeller@gmail.com> ``` On 10.08.2014 15:57, Stefan Beller wrote: > Found by scan.coverity.com (Id: 1127809) > > Signed-off-by: Stefan Beller > --- > remote.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/remote.c b/remote.c > index 3d6c86a..2c1458f 100644 > --- a/remote.c > +++ b/remote.c > @@ -1983,6 +1983,7 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb) > strbuf_addf(sb, > _(" (use \"git pull\" to merge the remote branch into yours)\n")); > } > + free(base); > return 1; > } > > Upon testing this one again, I get a warning remote.c: In function ‘format_tracking_info’: remote.c:1986:2: warning: passing argument 1 of ‘free’ discards ‘const’ qualifier from pointer target type [enabled by default] free(base); ^ In file included from git-compat-util.h:103:0, from cache.h:4, from remote.c:1: /usr/include/stdlib.h:483:13: note: expected ‘void *’ but argument is of type ‘const char *’ extern void free (void *__ptr) __THROW; ^ Please ignore this patch. ``` ## Jeff King, 2014-08-10 19:32 Subject: Re: [PATCH 1/2] remote.c: don't leak the base branch name in format_tracking_info Message-ID: <20140810193242.GA9886@peff.net> URL: https://gitlist.dev/e/20140810193242.GA9886%40peff.net In-Reply-To: <53E78C59.2010704@gmail.com> ``` On Sun, Aug 10, 2014 at 05:14:33PM +0200, Stefan Beller wrote: > On 10.08.2014 15:57, Stefan Beller wrote: > > Found by scan.coverity.com (Id: 1127809) > > > > Signed-off-by: Stefan Beller > > --- > > remote.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/remote.c b/remote.c > > index 3d6c86a..2c1458f 100644 > > --- a/remote.c > > +++ b/remote.c > > @@ -1983,6 +1983,7 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb) > > strbuf_addf(sb, > > _(" (use \"git pull\" to merge the remote branch into yours)\n")); > > } > > + free(base); > > return 1; > > } > > > > > > Upon testing this one again, I get a warning > remote.c: In function ‘format_tracking_info’: > remote.c:1986:2: warning: passing argument 1 of ‘free’ discards ‘const’ qualifier from pointer target type [enabled by default] > free(base); > ^ > In file included from git-compat-util.h:103:0, > from cache.h:4, > from remote.c:1: > /usr/include/stdlib.h:483:13: note: expected ‘void *’ but argument is of type ‘const char *’ > extern void free (void *__ptr) __THROW; > ^ > > Please ignore this patch. I think your patch is definitely fixing a leak; it's just that the existing code is a little sloppy. It does: const char *base; ... base = branch->merge[0]->dst; base = shorten_unambiguous_ref(base, 0); In the first assignment, "base" should be const, as we are pointing to somebody else's memory. But in the second, we use the same pointer to store newly allocated memory from shorten_unambiguous_ref. In the general case, you need two pointers to do this right. However, we don't actually look at "base" between the two assignments, so I think you could just do it as: char *base; ... base = shorten_unambiguous_ref(branch->merge[0]->dst, 0); -Peff ``` ## Stefan Beller, 2014-08-10 19:43 Subject: [PATCH] remote.c: don't leak the base branch name in format_tracking_info Message-ID: <1407699813-1460-1-git-send-email-stefanbeller@gmail.com> URL: https://gitlist.dev/e/1407699813-1460-1-git-send-email-stefanbeller%40gmail.com In-Reply-To: <20140810193242.GA9886@peff.net> ``` Found by scan.coverity.com (Id: 1127809) Signed-off-by: Stefan Beller --- remote.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/remote.c b/remote.c index 3d6c86a..894db09 100644 --- a/remote.c +++ b/remote.c @@ -1920,7 +1920,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs) int format_tracking_info(struct branch *branch, struct strbuf *sb) { int ours, theirs; - const char *base; + char *base; int upstream_is_gone = 0; switch (stat_tracking_info(branch, &ours, &theirs)) { @@ -1936,8 +1936,7 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb) break; } - base = branch->merge[0]->dst; - base = shorten_unambiguous_ref(base, 0); + base = shorten_unambiguous_ref(branch->merge[0]->dst, 0); if (upstream_is_gone) { strbuf_addf(sb, _("Your branch is based on '%s', but the upstream is gone.\n"), @@ -1983,6 +1982,7 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb) strbuf_addf(sb, _(" (use \"git pull\" to merge the remote branch into yours)\n")); } + free(base); return 1; } -- 2.1.0.rc2 ``` ## Junio C Hamano, 2014-08-10 23:03 Subject: Re: [PATCH 1/2] remote.c: don't leak the base branch name in format_tracking_info Message-ID: URL: https://gitlist.dev/e/xmqq7g2g7xrv.fsf%40gitster.dls.corp.google.com In-Reply-To: <53E78C59.2010704@gmail.com> ``` Stefan Beller writes: > On 10.08.2014 15:57, Stefan Beller wrote: >> Found by scan.coverity.com (Id: 1127809) >> >> Signed-off-by: Stefan Beller >> --- >> remote.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/remote.c b/remote.c >> index 3d6c86a..2c1458f 100644 >> --- a/remote.c >> +++ b/remote.c >> @@ -1983,6 +1983,7 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb) >> strbuf_addf(sb, >> _(" (use \"git pull\" to merge the remote branch into yours)\n")); >> } >> + free(base); >> return 1; >> } >> >> > > Upon testing this one again, I get a warning > remote.c: In function ‘format_tracking_info’: > remote.c:1986:2: warning: passing argument 1 of ‘free’ discards ‘const’ qualifier from pointer target type [enabled by default] > free(base); > ^ > ... > Please ignore this patch. It is perfectly fine to cast it to (char *) in this case, I think. The real culprit is that the functionà reuses the same "base" (which is a pointer into a constant region of memory) to receive the new copy allocated by shorten_unambiguous_ref(); the piece of memory returned by the callee belongs to this function, and it is perfectly fine if this function modifies the contents of it (which it doesn't happen to do). Storing the returned value to a variable of type "const char *" does not absolve it from the responsibility to free it (hence your patch). ```