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smtp.kernel.org (Postfix) with ESMTPSA id 1D9FDC433C7; Mon, 29 Jan 2024 12:43:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706532217; bh=qEaDcI77Zs3RXzEb9ijo5VEe7XOiy8LdZc2C7h7DSWk=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=up6YWHoRza7tFkwjjJNODxnPPVHLTOM4VqRApxtjkxQPp3QUqW/gS/Xvriv0eJTBK gb2cQFsuCUwelJMJu+UPsSgSxvckJe8H2810FzZ1hYTEc9Sttdf5QHnT4ouinjrczN +L8QwZeJYX48I6QIk31tqlv8+1VLq5J7hkm38s8UK9y7Uf1/ZW2IiXH85/zR9Ag6EX SyKhPlZK5NBJx53X+HnwYqyg5wQqzxRmdlg8NRAhn+z9bESsS/oFgvCMOSu36I7YQo MpcJfn5/9hyxSgce+wVsV9dtBQq4U22gzFBhkEZ76rypHNaZ07RqosiVFOTcBsUw9N P5VI/Y5tzFmLA== Message-ID: <1e4d080eb0d94b40f8fc5cce60a83391b9a2c2c3.camel@kernel.org> Subject: Re: [PATCH 2/2] netfs: Fix missing zero-length check in unbuffered write From: Jeff Layton To: David Howells , Christian Brauner Cc: Eric Van Hensbergen , Dominique Martinet , Matthew Wilcox , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, 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 klgooO6P DnU4uETyIlu8qqHF93V16kCPYAsg/WC2HqG7dcTZVHu4zexH4M5qZMXcFPaer12R7XDE066s4bsIiUxxGI9J8YXFVKW7kYEV9wLT8S81J0zsI4JwbwgWpwSCAhuy8aPqDURWhMugz484H8PHX+WlNOytpc0cWqqpAVKG1C0hNSVghjPDBVwG3u95h8i4ykrcJMYQQT62V4f/ZUIYDRJHQJCDQd3Gu8+WiWnuD4BxghG0RQaRhhVnUi2mgTL+PRHWC6X917ZIhTIh5eoDy6gF383zQfZ/dwYWAV7E9FBl6Wzou9C5jBcPRgWo24FGnqkN2SHLsngiWI1oynHJyGyX+7ogYcbll7HIaS8eUljKkpz5f095Ucg01xO107kOn+mBvhMFQtnEkYnc5VnGEi/PG0C7ASSafKVudyYcE X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 2024-01-29 at 09:49 +0000, David Howells wrote: > Fix netfs_unbuffered_write_iter() to return immediately if > generic_write_checks() returns 0, indicating there's nothing to write. > Note that netfs_file_write_iter() already does this. >=20 > Also, whilst we're at it, put in checks for the size being zero before we > even take the locks. Note that generic_write_checks() can still reduce t= he > size to zero, so we still need that check. >=20 > Without this, a warning similar to the following is logged to dmesg: >=20 > netfs: Zero-sized write [R=3D1b6da] >=20 > and the syscall fails with EIO, e.g.: >=20 > /sbin/ldconfig.real: Writing of cache extension data failed: Input/outpu= t error >=20 > This can be reproduced on 9p by: >=20 > xfs_io -f -c 'pwrite 0 0' /xfstest.test/foo >=20 > Fixes: 153a9961b551 ("netfs: Implement unbuffered/DIO write support") > Reported-by: Eric Van Hensbergen > Link: https://lore.kernel.org/r/ZbQUU6QKmIftKsmo@FV7GG9FTHL/ > Signed-off-by: David Howells > cc: Dominique Martinet > cc: Jeff Layton > cc: v9fs@lists.linux.dev > cc: linux_oss@crudebyte.com > cc: netfs@lists.linux.dev > cc: linux-fsdevel@vger.kernel.org > --- > fs/netfs/buffered_write.c | 3 +++ > fs/netfs/direct_write.c | 5 ++++- > 2 files changed, 7 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c > index a3059b3168fd..9a0d32e4b422 100644 > --- a/fs/netfs/buffered_write.c > +++ b/fs/netfs/buffered_write.c > @@ -477,6 +477,9 @@ ssize_t netfs_file_write_iter(struct kiocb *iocb, str= uct iov_iter *from) > =20 > _enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read= (inode)); > =20 > + if (!iov_iter_count(from)) > + return 0; > + > if ((iocb->ki_flags & IOCB_DIRECT) || > test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)) > return netfs_unbuffered_write_iter(iocb, from); > diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c > index 60a40d293c87..bee047e20f5d 100644 > --- a/fs/netfs/direct_write.c > +++ b/fs/netfs/direct_write.c > @@ -139,6 +139,9 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *ioc= b, struct iov_iter *from) > =20 > _enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read= (inode)); > =20 > + if (!iov_iter_count(from)) > + return 0; > + > trace_netfs_write_iter(iocb, from); > netfs_stat(&netfs_n_rh_dio_write); > =20 > @@ -146,7 +149,7 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *ioc= b, struct iov_iter *from) > if (ret < 0) > return ret; > ret =3D generic_write_checks(iocb, from); > - if (ret < 0) > + if (ret <=3D 0) > goto out; > ret =3D file_remove_privs(file); > if (ret < 0) >=20 Reviewed-by: Jeff Layton