neovim

commit a69c72063994f8e9064b6d9c9f280120423897b8
parent 8ba552bd59b0ed9f316ad1473126b603f35c912a
Author: Colin Watson <cjwatson@ubuntu.com>
Date:   Fri,  8 Mar 2024 21:49:06 +0000

fix(fileio): fix off-by-one in rename_with_tmp (#27780)

`_FORTIFY_SOURCE` on Ubuntu caught this, resulting in:

    [OLDTEST] Running test_rename
    Failed: test_rename :: Nvim exited with non-zero code
    Job exited with code 134
    Screen (23 lines)
    ================================================================================
    "test_rename.vim" "test_rename.vim" 120L, 3623B
    Executing Test_rename_copy()
    Executing Test_rename_dir_to_dir()
    Executing Test_rename_fails()
    Error detected while processing command line..script /<<BUILDDIR>>/neovim-0.9.5/test/old/testdir/runtest.vim[437]..function RunTheTest[44]..Test_rename_fails:
    line   17:
    E730: using List as a String
    line   18:
    E976: using Blob as a String
    Executing Test_rename_file_ignore_case()*** buffer overflow detected ***: terminated

`snprintf`'s second parameter should be no greater than the number of
remaining bytes in the allocated object.  We can see that this was off
by one, because in the simple case where `tail == tempname` (for a file
in the current directory), `rename_with_tmp` was passing `MAXPATHL + 2`
for an object allocated with a size of only `MAXPATHL + 1`.

Introduced in 5f1a153831d480180b2203120cff776d771ec1a4.
Diffstat:
M
src/nvim/fileio.c
 | 
2
+-

1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
@@ -2629,7 +2629,7 @@ static int rename_with_tmp(const char *const from, const char *const to)
   STRCPY(tempname, from);
   for (int n = 123; n < 99999; n++) {
     char *tail = path_tail(tempname);
-    snprintf(tail, (size_t)((MAXPATHL + 1) - (tail - tempname - 1)), "%d", n);
+    snprintf(tail, (size_t)((MAXPATHL + 1) - (tail - tempname)), "%d", n);
 
     if (!os_path_exists(tempname)) {
       if (os_rename(from, tempname) == OK) {