From 81dfa035891f0502674332ee97db348a16486de0 Mon Sep 17 00:00:00 2001 From: Hungyu Lin Date: Mon, 26 Oct 2026 01:57:38 +0000 Subject: [PATCH] fs: skip copy_file_range write limits when there is no data generic_copy_file_checks() reduces count to zero for a source offset at or beyond EOF, but still checks the destination write limits. If pos_out is at RLIMIT_FSIZE, this sends SIGXFSZ and returns -EFBIG even though there is no data to write. For example, GNU cat copying a 1024-byte regular file to another regular file with RLIMIT_FSIZE=1024 copies all bytes and is then killed by its next copy_file_range() call at EOF. A zero-length request can fail in the same way. Check write limits only when count is nonzero, as the ordinary write checks already do. Keep the other copy validation in place. Fixes: 96e6e8f4a68d ("vfs: add missing checks to copy_file_range") Cc: stable@vger.kernel.org Signed-off-by: Hungyu Lin Link: https://patch.msgid.link/20261026015738.46230-1-dennylin0707@gmail.com Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner (Amutable) --- fs/read_write.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/read_write.c b/fs/read_write.c index 4da3e553090b..676728310899 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1531,9 +1531,11 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in, else count = min(count, size_in - (uint64_t)pos_in); - ret = generic_write_check_limits(file_out, pos_out, &count); - if (ret) - return ret; + if (count) { + ret = generic_write_check_limits(file_out, pos_out, &count); + if (ret) + return ret; + } /* Don't allow overlapped copying within the same file. */ if (inode_in == inode_out &&