On Fri, 22 Aug 2025 19:23:35 +0200 Stefano Brivio
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.
Thanks. We already have https://lkml.kernel.org/r/20250821105806.1453833-1-wangzijie1@honor.com - does that look suitable?