[PATCH] alpha: objstrip: fix partial write() buffer pointer not advancing

[PATCH] alpha: objstrip: fix partial write() buffer pointer not advancing

[Maximilian Pezzullo via B4 Relay]

From: Maximilian Pezzullo <maximilianpezzullo@gmail.com>

In the main copy loop, on a partial write() the inner do-while
retried write(ofd, buf, n) always from the start of buf, while
only n was decremented.  This caused already-written data to be
re-written, corrupting the output file on systems where write()
returns less than the requested byte count.

Fix by introducing a pointer 'p' that tracks the current write
position within buf and advances it by nwritten on each iteration.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221159
Signed-off-by: Maximilian Pezzullo <maximilianpezzullo@gmail.com>
---
 arch/alpha/boot/tools/objstrip.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/alpha/boot/tools/objstrip.c b/arch/alpha/boot/tools/objstrip.c
index 7cf92d172dc..8da25c2584f 100644
--- a/arch/alpha/boot/tools/objstrip.c
+++ b/arch/alpha/boot/tools/objstrip.c
@@ -246,14 +246,18 @@ main (int argc, char *argv[])
 	    perror("read");
 	    exit(1);
 	}
-	do {
-	    nwritten = write(ofd, buf, n);
-	    if ((ssize_t) nwritten == -1) {
-		perror("write");
-		exit(1);
-	    }
-	    n -= nwritten;
-	} while (n > 0);
+	{
+	    char *p = buf;
+	    do {
+		nwritten = write(ofd, p, n);
+		if ((ssize_t) nwritten == -1) {
+		    perror("write");
+		    exit(1);
+		}
+		p += nwritten;
+		n -= nwritten;
+	    } while (n > 0);
+	}
     }
 
     if (pad) {

---
base-commit: af4e9ef3d78420feb8fe58cd9a1ab80c501b3c08
change-id: 20260303-alpha-fix-ce5f70ee801d

Best regards,
-- 
Maximilian Pezzullo <maximilianpezzullo@gmail.com>