ftruncate may only be called on regular files. This became broken in
a5f73a6dcd. Revert to the previous behaviour and pass O_TRUNC to the
initial open() call instead of truncating it with ftruncate().

Also we can call ftruncate() to the final size also when the file
previously didn't exist.

Fixes: a5f73a6dcd ("libfile: copy_file: explicitly truncate to final size")
Reported-by: Bastian Krause <[email protected]>
Signed-off-by: Sascha Hauer <[email protected]>
---
 lib/libfile.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/libfile.c b/lib/libfile.c
index 863b6833a5..20bb689a79 100644
--- a/lib/libfile.c
+++ b/lib/libfile.c
@@ -353,6 +353,10 @@ int copy_file(const char *src, const char *dst, int 
verbose)
                goto out;
        }
 
+       /* Set O_TRUNC only if file exists and is a regular file */
+       if (!s && S_ISREG(dststat.st_mode))
+               mode |= O_TRUNC;
+
        dstfd = open(dst, mode);
        if (dstfd < 0) {
                printf("could not open %s: %s\n", dst, errno_str());
@@ -360,17 +364,13 @@ int copy_file(const char *src, const char *dst, int 
verbose)
                goto out;
        }
 
-       ret = ftruncate(dstfd, 0);
-       if (ret)
-               goto out;
-
        ret = stat(src, &srcstat);
        if (ret)
                goto out;
 
        if (srcstat.st_size != FILESIZE_MAX) {
                discard_range(dstfd, srcstat.st_size, 0);
-               if (S_ISREG(dststat.st_mode)) {
+               if (s || S_ISREG(dststat.st_mode)) {
                        ret = ftruncate(dstfd, srcstat.st_size);
                        if (ret)
                                goto out;
-- 
2.28.0


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