From b29f4abcd4b3382fa746edd1d0562b7b48c9de60 Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Thu, 1 Aug 2024 22:10:28 +0200
Subject: [PATCH] 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: #15403

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

Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/ex_cmds2.c                       |   6 ++++--
 src/testdir/crash/dialog_changed_uaf | Bin 0 -> 552 bytes
 src/testdir/test_crash.vim           |   6 ++++++
 src/version.c                        |   2 ++
 4 files changed, 12 insertions(+), 2 deletions(-)
 create mode 100644 src/testdir/crash/dialog_changed_uaf

diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index ce30b8d39..0d76b3b27 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -197,9 +197,11 @@ dialog_changed(
 	// restore to empty when write failed
 	if (empty_bufname)
 	{
-	    VIM_CLEAR(buf->b_fname);
+	    // prevent double free
+	    if (buf->b_sfname != buf->b_ffname)
+		VIM_CLEAR(buf->b_sfname);
+	    buf->b_fname = NULL;
 	    VIM_CLEAR(buf->b_ffname);
-	    VIM_CLEAR(buf->b_sfname);
 	    unchanged(buf, TRUE, FALSE);
 	}
     }
diff --git a/src/testdir/crash/dialog_changed_uaf b/src/testdir/crash/dialog_changed_uaf
new file mode 100644
index 0000000000000000000000000000000000000000..e37d18d6daca107697bd19934b34054aa09e48a4
GIT binary patch
literal 552
zcmaKo!A{gb7=ZsSVA4N<B{3lzPeW6)o32GS;$lijP<BHgK%>z`lOEb_XQfzXmQI(h
zB_W$|Q|}&p0gqgG09c>IH^2vQY{3M*_}ymyN#^^0FRs_?L|EK)74X^j4ecMS-5Wsu
ztYZDu8)Q5_@S;j%$FkMAXqH#zri;;d{9}C0foYngn`Pg2S(e#t+di{xdkfcJZ#-YW
zy^nlM1x5l22mlTmYpSX&EiuOS8FOlh*A>`w+giMgG<?DGe<8rqNXqI7KIwEigL$IB
zcENdwQ&LVL;?c1<erFNvrbq)cdswKJZ<7}PPP=<^0EoUS&`Q@nH=R97Cj6%%8w@>s
z&=7u1Afp5YM_QX*rLJq5EF4;aQxkH;9>eHEzKnaxL*tp*h|1+s8TnTJhO{o5uB#zn
zR~QCGL;Dhtc_j}O>_TIY90vtWh~I;mP0>evFr-9~$(aE3+QLF>5@_F0c^amRVL}=2
z@%a6HJ$CRA;g^(h`U-#!`?(x=;2`@L|8M6}W#`bc?_}9&wo(+n4gHu4-b+ls|0hk=
buhVkxmBKq0EhW_}{Zl))e5nDWDZ=PC8xf-<

literal 0
HcmV?d00001

diff --git a/src/testdir/test_crash.vim b/src/testdir/test_crash.vim
index 29061aa42..9aef24502 100644
--- a/src/testdir/test_crash.vim
+++ b/src/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!
diff --git a/src/version.c b/src/version.c
index 0e49ebd7a..3ca600126 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    648,
 /**/
     647,
 /**/