From mboxrd@z Thu Jan 1 00:00:00 1970 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 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 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: AFVL566M6ZOGTHN4YULCKH3RXUIEF3A7 X-Message-ID-Hash: AFVL566M6ZOGTHN4YULCKH3RXUIEF3A7 X-MailFrom: sbrivio@passt.top X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Andrew Morton , wangzijie , Alexey Dobriyan , Christian Brauner , passt-dev@passt.top, Al Viro , Ye Bin , Alexei Starovoitov , "Rick P . Edgecombe" , "Kirill A . Shutemov" X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: 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=none pasta -- true [...] openat(AT_FDCWD, "/proc/net/tcp", O_RDONLY|O_CLOEXEC) = 12 openat(AT_FDCWD, "/proc/net/tcp6", O_RDONLY|O_CLOEXEC) = 13 lseek(12, 0, SEEK_SET) = -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek lseek(13, 0, SEEK_SET) = -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek openat(AT_FDCWD, "/proc/net/udp", O_RDONLY|O_CLOEXEC) = 14 openat(AT_FDCWD, "/proc/net/udp6", O_RDONLY|O_CLOEXEC) = 15 lseek(14, 0, SEEK_SET) = -1 ESPIPE (Illegal seek) lseek() failed on /proc/net file: Illegal seek lseek(15, 0, SEEK_SET) = -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 ones 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; } -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 |= 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 *, struct 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_entry *); +void pde_set_flags(struct proc_dir_entry *pde); 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 = &proc_net_seq_ops; p->seq_ops = ops; p->state_size = 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 = ops; p->state_size = state_size; p->write = 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 char *name, umode_t mode, pde_force_lookup(p); p->proc_ops = &proc_net_single_ops; p->single_show = 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(const char *name, umode_t mo p->proc_ops = &proc_net_single_ops; p->single_show = show; p->write = write; + pde_set_flags(p); return proc_register(parent, p); } EXPORT_SYMBOL_GPL(proc_create_net_single_write); -- 2.43.0