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([2405:201:682f:389d:a157:2060:c54e:fca0]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b08368eb9asm30624955ad.69.2026.03.20.06.06.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Mar 2026 06:06:23 -0700 (PDT) From: Deepanshu Kartikey To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+d31a3b77e5cba96b9f69@syzkaller.appspotmail.com, Deepanshu Kartikey Subject: [PATCH] splice: prevent deadlock when splicing a file to itself Date: Fri, 20 Mar 2026 18:36:15 +0530 Message-ID: <20260320130615.1109449-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When do_splice_direct_actor() is called with the same inode for both input and output files (either via the same fd or a dup'd fd), it causes a hung task in blkdev_write_iter(). The deadlock occurs because sendfile() calls do_splice_direct() which tries to acquire inode_lock_shared() for reading, while the write side already holds the same inode lock, causing the task to block indefinitely in rwsem_down_read_slowpath(). Fix this by checking if the input and output files share the same inode before proceeding, returning -EINVAL if they do. This mirrors the existing check in do_splice() for the pipe-to-pipe case where ipipe =3D=3D opipe. Reported-by: syzbot+d31a3b77e5cba96b9f69@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Dd31a3b77e5cba96b9f69 Tested-by: syzbot+d31a3b77e5cba96b9f69@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- fs/splice.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/splice.c b/fs/splice.c index 9d8f63e2fd1a..c0ad1859de34 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1199,6 +1199,9 @@ static ssize_t do_splice_direct_actor(struct file *in= , loff_t *ppos, if (unlikely(out->f_flags & O_APPEND)) return -EINVAL; =20 + /* Prevent deadlock when splicing a file to itself */ + if (file_inode(in) =3D=3D file_inode(out)) + return -EINVAL; ret =3D splice_direct_to_actor(in, &sd, actor); if (ret > 0) *ppos =3D sd.pos; --=20 2.43.0