# [PATCH] fetch-pack: Avoid memcpy() with src==dst 2 messages from 2008-12-06 to 2008-12-08. Participants: Thomas Rast, Junio C Hamano. Thread: https://gitlist.dev/t/16616 ## Thomas Rast, 2008-12-06 20:50 Subject: [PATCH] fetch-pack: Avoid memcpy() with src==dst Message-ID: <1228596609-12720-1-git-send-email-trast@student.ethz.ch> URL: https://gitlist.dev/e/1228596609-12720-1-git-send-email-trast%40student.ethz.ch ``` memcpy() may only be used for disjoint memory areas, but when invoked from cmd_fetch_pack(), we have my_args == &args. (The argument cannot be removed entirely because transport.c invokes with its own variable.) Signed-off-by: Thomas Rast --- Found this while valgrinding too much. builtin-fetch-pack.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/builtin-fetch-pack.c b/builtin-fetch-pack.c index 372bfa2..67fb80e 100644 --- a/builtin-fetch-pack.c +++ b/builtin-fetch-pack.c @@ -780,7 +780,8 @@ struct ref *fetch_pack(struct fetch_pack_args *my_args, struct ref *ref_cpy; fetch_pack_setup(); - memcpy(&args, my_args, sizeof(args)); + if (&args != my_args) + memcpy(&args, my_args, sizeof(args)); if (args.depth > 0) { if (stat(git_path("shallow"), &st)) st.st_mtime = 0; -- tg: (7f705dc..) t/fp-memcpy-fix (depends on: origin/master) ``` ## Junio C Hamano, 2008-12-08 02:47 Subject: Re: [PATCH] fetch-pack: Avoid memcpy() with src==dst Message-ID: <7viqpvbcxy.fsf@gitster.siamese.dyndns.org> URL: https://gitlist.dev/e/7viqpvbcxy.fsf%40gitster.siamese.dyndns.org In-Reply-To: <1228596609-12720-1-git-send-email-trast@student.ethz.ch> ``` Thomas Rast writes: > memcpy() may only be used for disjoint memory areas, but when invoked > from cmd_fetch_pack(), we have my_args == &args. (The argument cannot > be removed entirely because transport.c invokes with its own > variable.) It makes me wonder if it might be a better fix to abolish the use of file scoped global "args" and pass a pointer to "struct fetch_pack_args" throughout the callchain instead. In the current code, cmd_fetch_pack() is the only caller that passes &args to this function, but it is not so implausible to have a future callchain that makes two calls to cmd_fetch_pack(), perhaps implementing some sort of alias to fetch from multiple places, would horribly break without such a fix, because cmd_fetch_pack() assumes that args is in its pristine state. I'll apply this to 'maint' and merge it up, because the patch is independent of the above issue. Thanks. ```