From: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Date: Wed, 14 May 2025 18:16:52 +0000 (+0200)
Subject: patch 9.1.1387: memory leak when buflist_new() fails to reuse curbuf
X-Git-Tag: v9.1.1387^0
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0077282c8209e5a3893d74a0176ab21895c5de4e;p=thirdparty%2Fvim.git

patch 9.1.1387: memory leak when buflist_new() fails to reuse curbuf

Problem:  buflist_new() leaks ffname and fails to reuse curbuf when
          autocommands from buf_freeall change curbuf. Plus, a new
          buffer is not allocated in this case, despite what the comment
          above claims.
Solution: Remove the condition so ffname is not leaked and so a new
          buffer is allocated like before v8.2.4791. It should not be
          possible for undo_ftplugin or buf_freeall autocommands to
          delete the buffer as they set b_locked, but to stay consistent
          with other uses of buf_freeall, guard against that anyway
          (Sean Dewar).

Note that buf is set to NULL if it was deleted to guard against the (rare)
possibility of messing up the "buf != curbuf" condition below if a new buffer
happens to be allocated at the same address.

closes: #17319

Signed-off-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/src/buffer.c b/src/buffer.c
index b4481b2f13..49ec77c7b1 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2220,13 +2220,14 @@ buflist_new(
     buf = NULL;
     if ((flags & BLN_CURBUF) && curbuf_reusable())
     {
+	bufref_T bufref;
+
 	buf = curbuf;
+	set_bufref(&bufref, buf);
 	trigger_undo_ftplugin(buf, curwin);
 	// It's like this buffer is deleted.  Watch out for autocommands that
 	// change curbuf!  If that happens, allocate a new buffer anyway.
 	buf_freeall(buf, BFA_WIPE | BFA_DEL);
-	if (buf != curbuf)   // autocommands deleted the buffer!
-	    return NULL;
 #ifdef FEAT_EVAL
 	if (aborting())		// autocmds may abort script processing
 	{
@@ -2234,6 +2235,8 @@ buflist_new(
 	    return NULL;
 	}
 #endif
+	if (!bufref_valid(&bufref))
+	    buf = NULL;		// buf was deleted; allocate a new buffer
     }
     if (buf != curbuf || curbuf == NULL)
     {
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index db5558304d..26f7145652 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -5390,4 +5390,29 @@ func Test_eventignorewin_non_current()
   %bw!
 endfunc
 
+func Test_reuse_curbuf_leak()
+  new bar
+  let s:bar_buf = bufnr()
+  augroup testing
+    autocmd!
+    autocmd BufDelete * ++once let s:triggered = 1 | execute s:bar_buf 'buffer'
+  augroup END
+  enew
+  let empty_buf = bufnr()
+
+  " Old curbuf should be reused, firing BufDelete. As BufDelete changes curbuf,
+  " reusing the buffer would fail and leak the ffname.
+  edit foo
+  call assert_equal(1, s:triggered)
+  " Wasn't reused because the buffer changed, but buffer "foo" is still created.
+  call assert_equal(1, bufexists(empty_buf))
+  call assert_notequal(empty_buf, bufnr())
+  call assert_equal('foo', bufname())
+  call assert_equal('bar', bufname(s:bar_buf))
+
+  unlet! s:bar_buf s:triggered
+  call CleanUpTestAuGroup()
+  %bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 78a6e7b7c0..7e6e862de6 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 */
+/**/
+    1387,
 /**/
     1386,
 /**/