From: Andrei Tatar <andrei@unikraft.io>
Date: Tue, 18 Mar 2025 16:43:38 +0000 (+0100)
Subject: lib/posix-fdio: Fix lseek relative from file end
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=43829daf760ea73fb7d03a18e60c1a8590ec07d9;p=unikraft%2Funikraft.git

lib/posix-fdio: Fix lseek relative from file end

This change fixes a bug in lseek where the file cursor was always set to
the end of file on SEEK_END, ignoring any passed-in offset.

Signed-off-by: Andrei Tatar <andrei@unikraft.io>
Approved-by: Sergiu Moga <sergiu@unikraft.io>
Reviewed-by: Sergiu Moga <sergiu@unikraft.io>
GitHub-Closes: #1602
---

diff --git a/lib/posix-fdio/fdio.c b/lib/posix-fdio/fdio.c
index 0d4b50b5c..ea07b6480 100644
--- a/lib/posix-fdio/fdio.c
+++ b/lib/posix-fdio/fdio.c
@@ -417,12 +417,17 @@ off_t uk_sys_lseek(struct uk_ofile *of, off_t offset, int whence)
 	_of_lock(of);
 	if (whence == SEEK_END) {
 		const struct uk_file *f = of->file;
+		ssize_t eof;
 
 		if (iolock)
 			uk_file_rlock(f);
-		offset = fdio_get_eof(f);
+		eof = fdio_get_eof(f);
 		if (iolock)
 			uk_file_runlock(f);
+		if (eof >= 0)
+			offset += eof;
+		else
+			offset = eof;
 	} else if (whence == SEEK_CUR) {
 		offset += of->pos;
 	}