From nobody Fri Oct 3 23:02:06 2025 Received: from passt.top (passt.top [88.198.0.164]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D70335948; Fri, 22 Aug 2025 17:33:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=88.198.0.164 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755884002; cv=none; b=bfIwToBBsvbwxD0cLPhikJCo6cxu0TXTKPYbJU8vK+RybJRMZ60NGS7Icu5bi9je7aXa4MUb1ffsbOkifV8QFMu8jiA9p8Nbg7+5fTPmwluEZALn4Gx6DmdrbHrvwrYhCH3huQAZu2Z8ubovuJBp/K9Uvn1ZpZrSuvXQCY0wNv0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755884002; c=relaxed/simple; bh=Ep+12uNxJtRBwkg/6WXOn5HwUmXIfedla1HYoJDu6sc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=toW7WNgSy0XR3PPRyd3yIRFtC8zY43Il/4cNkt6qrhiOs7FeoYJGwYPppd90TLFIrw61g15OocDCfge9uOLAHiHy4y/MG0EJq4fiTg+iTCv+mDbmwnwDHxOZDvLqOIL/cal3XVsQ+94WdLr5s5NygcKz/DUIK6mu9mRnOcCGp60= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=passt.top; arc=none smtp.client-ip=88.198.0.164 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=passt.top Received: by passt.top (Postfix, from userid 1000) id 9262A5A027A; Fri, 22 Aug 2025 19:23:35 +0200 (CEST) From: Stefano Brivio To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , wangzijie , Alexey Dobriyan , Christian Brauner , passt-dev@passt.top, Al Viro , Ye Bin , Alexei Starovoitov , "Rick P . Edgecombe" , "Kirill A . Shutemov" Subject: [PATCH] proc: Bring back lseek() operations for /proc/net entries Date: Fri, 22 Aug 2025 19:23:35 +0200 Message-ID: <20250822172335.3187858-1-sbrivio@redhat.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" Commit ff7ec8dc1b64 ("proc: use the same treatment to check proc_lseek as ones for proc_read_iter et.al") breaks lseek() for all /proc/net entries, as shown for instance by pasta(1), a user-mode network implementation using those entries to scan for bound ports: $ strace -e openat,lseek -e s=3Dnone pasta -- true [...] openat(AT_FDCWD, "/proc/net/tcp", O_RDONLY|O_CLOEXEC) =3D 12 openat(AT_FDCWD, "/proc/net/tcp6", O_RDONLY|O_CLOEXEC) =3D 13 lseek(12, 0, SEEK_SET) =3D -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek lseek(13, 0, SEEK_SET) =3D -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek openat(AT_FDCWD, "/proc/net/udp", O_RDONLY|O_CLOEXEC) =3D 14 openat(AT_FDCWD, "/proc/net/udp6", O_RDONLY|O_CLOEXEC) =3D 15 lseek(14, 0, SEEK_SET) =3D -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek lseek(15, 0, SEEK_SET) =3D -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek [...] That's because PROC_ENTRY_proc_lseek isn't set for /proc/net entries, and it's now mandatory for lseek(). In fact, flags aren't set at all for those entries because pde_set_flags() isn't called for them. As commit d919b33dafb3 ("proc: faster open/read/close with "permanent" files") introduced flags for procfs directory entries, along with the pde_set_flags() helper, they weren't relevant for /proc/net entries, so the lack of pde_set_flags() calls in proc_create_net_*() functions was harmless. Now that the calls are strictly needed for lseek() functionality, add them. Fixes: ff7ec8dc1b64 ("proc: use the same treatment to check proc_lseek as o= nes for proc_read_iter et.al") Signed-off-by: Stefano Brivio --- fs/proc/generic.c | 2 +- fs/proc/internal.h | 1 + fs/proc/proc_net.c | 4 ++++ 3 files changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 76e800e38c8f..57ec5e385d1b 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -561,7 +561,7 @@ struct proc_dir_entry *proc_create_reg(const char *name= , umode_t mode, return p; } =20 -static void pde_set_flags(struct proc_dir_entry *pde) +void pde_set_flags(struct proc_dir_entry *pde) { if (pde->proc_ops->proc_flags & PROC_ENTRY_PERMANENT) pde->flags |=3D PROC_ENTRY_PERMANENT; diff --git a/fs/proc/internal.h b/fs/proc/internal.h index e737401d7383..a358974f14d2 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -284,6 +284,7 @@ extern struct dentry *proc_lookup(struct inode *, struc= t dentry *, unsigned int) struct dentry *proc_lookup_de(struct inode *, struct dentry *, struct proc= _dir_entry *); extern int proc_readdir(struct file *, struct dir_context *); int proc_readdir_de(struct file *, struct dir_context *, struct proc_dir_e= ntry *); +void pde_set_flags(struct proc_dir_entry *pde); =20 static inline void pde_get(struct proc_dir_entry *pde) { diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c index 52f0b75cbce2..20bc7481b02c 100644 --- a/fs/proc/proc_net.c +++ b/fs/proc/proc_net.c @@ -124,6 +124,7 @@ struct proc_dir_entry *proc_create_net_data(const char = *name, umode_t mode, p->proc_ops =3D &proc_net_seq_ops; p->seq_ops =3D ops; p->state_size =3D state_size; + pde_set_flags(p); return proc_register(parent, p); } EXPORT_SYMBOL_GPL(proc_create_net_data); @@ -170,6 +171,7 @@ struct proc_dir_entry *proc_create_net_data_write(const= char *name, umode_t mode p->seq_ops =3D ops; p->state_size =3D state_size; p->write =3D write; + pde_set_flags(p); return proc_register(parent, p); } EXPORT_SYMBOL_GPL(proc_create_net_data_write); @@ -217,6 +219,7 @@ struct proc_dir_entry *proc_create_net_single(const cha= r *name, umode_t mode, pde_force_lookup(p); p->proc_ops =3D &proc_net_single_ops; p->single_show =3D show; + pde_set_flags(p); return proc_register(parent, p); } EXPORT_SYMBOL_GPL(proc_create_net_single); @@ -261,6 +264,7 @@ struct proc_dir_entry *proc_create_net_single_write(con= st char *name, umode_t mo p->proc_ops =3D &proc_net_single_ops; p->single_show =3D show; p->write =3D write; + pde_set_flags(p); return proc_register(parent, p); } EXPORT_SYMBOL_GPL(proc_create_net_single_write); --=20 2.43.0