Re: git pull --set-upstream segfaults on branchless repo.
From: Jan Pokorný <hidden>
Date: 2021-07-19 10:12:06
Hello, Clemens Fruhwirth píše v Po 05. 07. 2021 v 17:46 +0200:
What did you do before the bug happened? (Steps to reproduce your
issue)
Run "git pull origin nixos-unstable --rebase --set-upstream"
on a repo that had no branch set, e.g. when running "git branch" gave
"* (no branch)"
What did you expect to happen? (Expected behavior)
Pull from upstream and set upstream.
What happened instead? (Actual behavior)
Segfault with the following trace:
(gdb) bt
#0 0x000000000044a8c9 in do_fetch (transport=0x2557920, rs=rs@entry=0x7ffd42335c00) at builtin/fetch.c:1568
#1 0x000000000044ac61 in fetch_one (remote=<optimized out>, argc=1110662144, argv=0x7ffd42335fc8, prune_tags_ok=<optimized out>, use_stdin_refspecs=0) at builtin/fetch.c:1892
#2 0x000000000044af15 in cmd_fetch (argc=0, argv=0x7ffd42335fc8, prefix=0x0) at builtin/fetch.c:1992
#3 0x0000000000406354 in run_builtin (p=0x70d3e0 <commands+960>, argc=argc@entry=5, argv=argv@entry=0x7ffd42335fc0) at git.c:453
#4 0x00000000004065c3 in handle_builtin (argc=5, argv=0x7ffd42335fc0) at git.c:704
#5 0x0000000000407c4a in run_argv (argcp=argcp@entry=0x7ffd42335e8c, argv=argv@entry=0x7ffd42335e80) at git.c:771
#6 0x00000000004080a4 in cmd_main (argc=<optimized out>, argc@entry=6, argv=<optimized out>, argv@entry=0x7ffd42335fb8) at git.c:902
#7 0x00000000004c614c in main (argc=6, argv=0x7ffd42335fb8) at common-main.c:52
(gdb) p branch
$1 = (struct branch *) 0x0
What's different between what you expected and what actually happened?
Not segfault
Anything else you want to add:
Dropping the "--set-upstream" makes the segfault go away. Looking at
builtin/fetch.c around L1568 I see,
if (set_upstream) {
struct branch *branch = branch_get("HEAD");
[..]
if (source_ref) {
if (!strcmp(source_ref->name, "HEAD") ||
starts_with(source_ref->name, "refs/heads/"))
install_branch_config(0,
branch->name, // <- SEGFAULT HERE
transport->remote->name,
source_ref->name);
[..]
}
}
It's rather clear that branch is just NULL from the gdb session above,
and the branch->name dereference fails.
It might be useful to catch branch == NULL.
Please review the rest of the bug report below.
You can delete any lines you don't wish to share.
[System Info]
git version:
git version 2.31.1
[...]observed something pretty similar on Fedora, with both git-2.32.0-0.3.rc2.fc35.x86_64 and git-2.32.0-1.fc35.x86_64, e.g.: $ git clone https://github.com/git/git.git [...] $ cd git $ git checkout --detach v2.1.0 HEAD is now at 6c4ab27f23 Git 2.1 $ git pull --set-upstream origin master From https://github.com/git/git * branch master -> FETCH_HEAD error: fetch died of signal 11 1625 if (source_ref) { 1626 if (!strcmp(source_ref->name, "HEAD") || 1627 starts_with(source_ref->name, "refs/heads/")) =>1628 install_branch_config(0, 1629 branch->name, 1630 transport->remote->name, 1631 source_ref->name); (gdb) p branch $1 = <optimized out> (gdb) p branch->name value has been optimized out 0x000055b5bceba921 <+8705>: nopl 0x0(%rax) 0x000055b5bceba928 <+8712>: mov (%rsp),%rax => 0x000055b5bceba92c <+8716>: mov (%r8),%rsi 0x000055b5bceba92f <+8719>: xor %edi,%edi 0x000055b5bceba931 <+8721>: mov 0x8(%rax),%rax 0x000055b5bceba935 <+8725>: mov 0x10(%rax),%rdx 0x000055b5bceba939 <+8729>: call 0x55b5bcf75d40 <install_branch_config> (gdb) info registers r8 rsi r8 0x0 0 rsi 0x55b5bdbe430b 94239060804363 This is just a generic reproducer; original use case revolved around the use of submodules (also happened to be in a detached state within, "--set-upstream" attempt was then my rushed response to "You are not currently on a branch." error message on a plain pull there).
(Please cc me on replies, not subscribe to the mailing list).
(ditto, please) -- poki