From 6967c08840bedfecc54884af815b75ff7ab7af7b Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Sat, 3 Aug 2024 08:13:20 +0800
Subject: [PATCH] vim-patch:9.1.0648: [security] double-free in
 dialog_changed()

Problem:  [security] double-free in dialog_changed()
          (SuyueGuo)
Solution: Only clear pointer b_sfname pointer, if it is different
          than the b_ffname pointer.  Don't try to free b_fname,
          set it to NULL instead.

fixes: vim/vim#15403

Github Advisory:
https://github.com/vim/vim/security/advisories/GHSA-46pw-v7qw-xc2f

https://github.com/vim/vim/commit/b29f4abcd4b3382fa746edd1d0562b7b48c9de60

Co-authored-by: Christian Brabandt <cb@256bit.org>
---
 src/nvim/ex_cmds2.c                       |   7 +++++--
 test/functional/legacy/crash_spec.lua     |  12 ++++++++++++
 test/old/testdir/crash/dialog_changed_uaf | Bin 0 -> 552 bytes
 test/old/testdir/test_crash.vim           |   6 ++++++
 4 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 test/old/testdir/crash/dialog_changed_uaf

diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index a602719f6d..b62bb8b42a 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -227,9 +227,12 @@ void dialog_changed(buf_T *buf, bool checkall)
 
     // restore to empty when write failed
     if (empty_bufname) {
-      XFREE_CLEAR(buf->b_fname);
+      // prevent double free
+      if (buf->b_sfname != buf->b_ffname) {
+        XFREE_CLEAR(buf->b_sfname);
+      }
+      buf->b_fname = NULL;
       XFREE_CLEAR(buf->b_ffname);
-      XFREE_CLEAR(buf->b_sfname);
       unchanged(buf, true, false);
     }
   } else if (ret == VIM_NO) {
diff --git a/test/functional/legacy/crash_spec.lua b/test/functional/legacy/crash_spec.lua
index e72c3a512a..b63b3146f4 100644
--- a/test/functional/legacy/crash_spec.lua
+++ b/test/functional/legacy/crash_spec.lua
@@ -8,6 +8,7 @@ local eq = t.eq
 local eval = n.eval
 local exec = n.exec
 local feed = n.feed
+local pcall_err = t.pcall_err
 
 before_each(clear)
 
@@ -51,3 +52,14 @@ it('no crash when closing window with tag in loclist', function()
   eq(0, eval('bufexists(g:qf_bufnr)'))
   assert_alive()
 end)
+
+it('no crash when writing "Untitled" file fails', function()
+  t.mkdir('Untitled')
+  finally(function()
+    vim.uv.fs_rmdir('Untitled')
+  end)
+  feed('ifoobar')
+  command('set bufhidden=unload')
+  eq('Vim(enew):E502: "Untitled" is a directory', pcall_err(command, 'confirm enew'))
+  assert_alive()
+end)
diff --git a/test/old/testdir/crash/dialog_changed_uaf b/test/old/testdir/crash/dialog_changed_uaf
new file mode 100644
index 0000000000000000000000000000000000000000..e37d18d6daca107697bd19934b34054aa09e48a4
GIT binary patch
literal 552
zcmYc+($>~iD7MN^NMK}0&O73%gaWL>A%NlkCv`6EkO;24{G!~%90@}|D}PS09D#fZ
zF<y|=;lqy(gF&vYuC78-Rn>~{ys9dHSAYKv{{H?xT<)QsPVNZtoMf)@Vy>KG1`tqS
zVBjh>bmrt_G&j%7%gf5ki_s`aOe*FwOK?>xvgS(749w%o%V$X8VruyRU%igYG%PHv
zR8fJE!50L!W^%Fq|If<B#Z^{aT%B&Ez?D?am72n(o5lrlDnG(YCdghBhHw}da%M9!
zxRg8hn8jqIDljKoWagDtBy#B(7AF@eFjS=~a24lsrD_N`q$VWj>gHuuSf#{h6#s9?
zGiGS0%rDB7D$&<+)HTfE=V#*Q%J)go)m3mgWR{Si#KpjsRIH_y%B7_=Jw-v0k%2*>
zIPaiRo<U3uS8-~ILUI}dpI31Kmr7|xszR{>3ttL@iiVz^3kySPffi?ed1kpuW=U#Z
zep-G}wyH`|3|Ao+!@vLk|MPxiU`VYfC{kcxNMwlN%Ihk^7v?z<euY;4Y*kgwRkk1>
zMrI}#<rn9tmFOlHK)uGP0`{7&f{QK4-HZ$jOeN|cRk~e^Q%i!B81hofxfmJ%8xf-<

literal 0
HcmV?d00001

diff --git a/test/old/testdir/test_crash.vim b/test/old/testdir/test_crash.vim
index 29061aa423..9aef245026 100644
--- a/test/old/testdir/test_crash.vim
+++ b/test/old/testdir/test_crash.vim
@@ -196,6 +196,12 @@ func Test_crash1_3()
   call term_sendkeys(buf, args)
   call TermWait(buf, 50)
 
+  let file = 'crash/dialog_changed_uaf'
+  let cmn_args = "%s -u NONE -i NONE -n -e -s -S %s -c ':qa!'\<cr>"
+  let args = printf(cmn_args, vim, file)
+  call term_sendkeys(buf, args)
+  call TermWait(buf, 150)
+
   " clean up
   exe buf .. "bw!"
   bw!