From: Giuseppe Scrivano <gscrivan@redhat.com> To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, containers@lists.linux-foundation.org, linux@rasmusvillemoes.dk, viro@zeniv.linux.org.uk Subject: [PATCH v2 1/2] fs, close_range: add flag CLOSE_RANGE_CLOEXEC Date: Mon, 19 Oct 2020 12:26:53 +0200 [thread overview] Message-ID: <20201019102654.16642-2-gscrivan@redhat.com> (raw) In-Reply-To: <20201019102654.16642-1-gscrivan@redhat.com> When the flag CLOSE_RANGE_CLOEXEC is set, close_range doesn't immediately close the files but it sets the close-on-exec bit. It is useful for e.g. container runtimes that usually install a seccomp profile "as late as possible" before execv'ing the container process itself. The container runtime could either do: 1 2 - install_seccomp_profile(); - close_range(MIN_FD, MAX_INT, 0); - close_range(MIN_FD, MAX_INT, 0); - install_seccomp_profile(); - execve(...); - execve(...); Both alternative have some disadvantages. In the first variant the seccomp_profile cannot block the close_range syscall, as well as opendir/read/close/... for the fallback on older kernels). In the second variant, close_range() can be used only on the fds that are not going to be needed by the runtime anymore, and it must be potentially called multiple times to account for the different ranges that must be closed. Using close_range(..., ..., CLOSE_RANGE_CLOEXEC) solves these issues. The runtime is able to use the open fds and the seccomp profile could block close_range() and the syscalls used for its fallback. Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com> --- fs/file.c | 44 ++++++++++++++++++++++++-------- include/uapi/linux/close_range.h | 3 +++ 2 files changed, 37 insertions(+), 10 deletions(-) diff --git a/fs/file.c b/fs/file.c index 21c0893f2f1d..0295d4f7c5ef 100644 --- a/fs/file.c +++ b/fs/file.c @@ -672,6 +672,35 @@ int __close_fd(struct files_struct *files, unsigned fd) } EXPORT_SYMBOL(__close_fd); /* for ksys_close() */ +static inline void __range_cloexec(struct files_struct *cur_fds, + unsigned int fd, unsigned int max_fd) +{ + struct fdtable *fdt; + + if (fd > max_fd) + return; + + spin_lock(&cur_fds->file_lock); + fdt = files_fdtable(cur_fds); + bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1); + spin_unlock(&cur_fds->file_lock); +} + +static inline void __range_close(struct files_struct *cur_fds, unsigned int fd, + unsigned int max_fd) +{ + while (fd <= max_fd) { + struct file *file; + + file = pick_file(cur_fds, fd++); + if (!file) + continue; + + filp_close(file, cur_fds); + cond_resched(); + } +} + /** * __close_range() - Close all file descriptors in a given range. * @@ -687,7 +716,7 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) struct task_struct *me = current; struct files_struct *cur_fds = me->files, *fds = NULL; - if (flags & ~CLOSE_RANGE_UNSHARE) + if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC)) return -EINVAL; if (fd > max_fd) @@ -725,16 +754,11 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) } max_fd = min(max_fd, cur_max); - while (fd <= max_fd) { - struct file *file; - file = pick_file(cur_fds, fd++); - if (!file) - continue; - - filp_close(file, cur_fds); - cond_resched(); - } + if (flags & CLOSE_RANGE_CLOEXEC) + __range_cloexec(cur_fds, fd, max_fd); + else + __range_close(cur_fds, fd, max_fd); if (fds) { /* diff --git a/include/uapi/linux/close_range.h b/include/uapi/linux/close_range.h index 6928a9fdee3c..2d804281554c 100644 --- a/include/uapi/linux/close_range.h +++ b/include/uapi/linux/close_range.h @@ -5,5 +5,8 @@ /* Unshare the file descriptor table before closing file descriptors. */ #define CLOSE_RANGE_UNSHARE (1U << 1) +/* Set the FD_CLOEXEC bit instead of closing the file descriptor. */ +#define CLOSE_RANGE_CLOEXEC (1U << 2) + #endif /* _UAPI_LINUX_CLOSE_RANGE_H */ -- 2.26.2 _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers
WARNING: multiple messages have this Message-ID (diff)
From: Giuseppe Scrivano <gscrivan@redhat.com> To: linux-kernel@vger.kernel.org Cc: linux@rasmusvillemoes.dk, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, christian.brauner@ubuntu.com, containers@lists.linux-foundation.org Subject: [PATCH v2 1/2] fs, close_range: add flag CLOSE_RANGE_CLOEXEC Date: Mon, 19 Oct 2020 12:26:53 +0200 [thread overview] Message-ID: <20201019102654.16642-2-gscrivan@redhat.com> (raw) In-Reply-To: <20201019102654.16642-1-gscrivan@redhat.com> When the flag CLOSE_RANGE_CLOEXEC is set, close_range doesn't immediately close the files but it sets the close-on-exec bit. It is useful for e.g. container runtimes that usually install a seccomp profile "as late as possible" before execv'ing the container process itself. The container runtime could either do: 1 2 - install_seccomp_profile(); - close_range(MIN_FD, MAX_INT, 0); - close_range(MIN_FD, MAX_INT, 0); - install_seccomp_profile(); - execve(...); - execve(...); Both alternative have some disadvantages. In the first variant the seccomp_profile cannot block the close_range syscall, as well as opendir/read/close/... for the fallback on older kernels). In the second variant, close_range() can be used only on the fds that are not going to be needed by the runtime anymore, and it must be potentially called multiple times to account for the different ranges that must be closed. Using close_range(..., ..., CLOSE_RANGE_CLOEXEC) solves these issues. The runtime is able to use the open fds and the seccomp profile could block close_range() and the syscalls used for its fallback. Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com> --- fs/file.c | 44 ++++++++++++++++++++++++-------- include/uapi/linux/close_range.h | 3 +++ 2 files changed, 37 insertions(+), 10 deletions(-) diff --git a/fs/file.c b/fs/file.c index 21c0893f2f1d..0295d4f7c5ef 100644 --- a/fs/file.c +++ b/fs/file.c @@ -672,6 +672,35 @@ int __close_fd(struct files_struct *files, unsigned fd) } EXPORT_SYMBOL(__close_fd); /* for ksys_close() */ +static inline void __range_cloexec(struct files_struct *cur_fds, + unsigned int fd, unsigned int max_fd) +{ + struct fdtable *fdt; + + if (fd > max_fd) + return; + + spin_lock(&cur_fds->file_lock); + fdt = files_fdtable(cur_fds); + bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1); + spin_unlock(&cur_fds->file_lock); +} + +static inline void __range_close(struct files_struct *cur_fds, unsigned int fd, + unsigned int max_fd) +{ + while (fd <= max_fd) { + struct file *file; + + file = pick_file(cur_fds, fd++); + if (!file) + continue; + + filp_close(file, cur_fds); + cond_resched(); + } +} + /** * __close_range() - Close all file descriptors in a given range. * @@ -687,7 +716,7 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) struct task_struct *me = current; struct files_struct *cur_fds = me->files, *fds = NULL; - if (flags & ~CLOSE_RANGE_UNSHARE) + if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC)) return -EINVAL; if (fd > max_fd) @@ -725,16 +754,11 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) } max_fd = min(max_fd, cur_max); - while (fd <= max_fd) { - struct file *file; - file = pick_file(cur_fds, fd++); - if (!file) - continue; - - filp_close(file, cur_fds); - cond_resched(); - } + if (flags & CLOSE_RANGE_CLOEXEC) + __range_cloexec(cur_fds, fd, max_fd); + else + __range_close(cur_fds, fd, max_fd); if (fds) { /* diff --git a/include/uapi/linux/close_range.h b/include/uapi/linux/close_range.h index 6928a9fdee3c..2d804281554c 100644 --- a/include/uapi/linux/close_range.h +++ b/include/uapi/linux/close_range.h @@ -5,5 +5,8 @@ /* Unshare the file descriptor table before closing file descriptors. */ #define CLOSE_RANGE_UNSHARE (1U << 1) +/* Set the FD_CLOEXEC bit instead of closing the file descriptor. */ +#define CLOSE_RANGE_CLOEXEC (1U << 2) + #endif /* _UAPI_LINUX_CLOSE_RANGE_H */ -- 2.26.2
next prev parent reply other threads:[~2020-10-19 10:27 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-19 10:26 [PATCH v2 0/2] fs, close_range: add flag CLOSE_RANGE_CLOEXEC Giuseppe Scrivano 2020-10-19 10:26 ` Giuseppe Scrivano 2020-10-19 10:26 ` Giuseppe Scrivano [this message] 2020-10-19 10:26 ` [PATCH v2 1/2] " Giuseppe Scrivano 2020-10-20 14:26 ` Christian Brauner 2020-10-20 14:26 ` Christian Brauner 2020-10-19 10:26 ` [PATCH v2 2/2] selftests: add tests for CLOSE_RANGE_CLOEXEC Giuseppe Scrivano 2020-10-19 10:26 ` Giuseppe Scrivano 2020-10-20 14:32 ` Christian Brauner 2020-10-20 14:32 ` Christian Brauner 2020-10-29 15:38 ` [PATCH v2 0/2] fs, close_range: add flag CLOSE_RANGE_CLOEXEC Christian Brauner 2020-10-29 15:38 ` Christian Brauner 2020-10-29 16:47 ` Giuseppe Scrivano 2020-10-29 16:47 ` Giuseppe Scrivano 2020-11-18 10:02 ` Christian Brauner 2020-11-18 10:02 ` Christian Brauner
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20201019102654.16642-2-gscrivan@redhat.com \ --to=gscrivan@redhat.com \ --cc=containers@lists.linux-foundation.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux@rasmusvillemoes.dk \ --cc=viro@zeniv.linux.org.uk \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.