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Date: Fri, 20 Nov 2020 17:14:36 -0600 From: "Eric W. Biederman" <ebiederm@...ssion.com> To: linux-kernel@...r.kernel.org Cc: linux-fsdevel@...r.kernel.org, criu@...nvz.org, bpf@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <christian.brauner@...ntu.com>, Oleg Nesterov <oleg@...hat.com>, Cyrill Gorcunov <gorcunov@...il.com>, Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>, Daniel P . Berrangé <berrange@...hat.com>, Jeff Layton <jlayton@...hat.com>, Miklos Szeredi <miklos@...redi.hu>, Matthew Wilcox <willy@...radead.org>, "J. Bruce Fields" <bfields@...ldses.org>, Trond Myklebust <trond.myklebust@...merspace.com>, Chris Wright <chrisw@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, "Eric W. Biederman" <ebiederm@...ssion.com> Subject: [PATCH v2 19/24] file: In f_dupfd read RLIMIT_NOFILE once. Simplify the code, and remove the chance of races by reading RLIMIT_NOFILE only once in f_dupfd. Pass the read value of RLIMIT_NOFILE into alloc_fd which is the other location the rlimit was read in f_dupfd. As f_dupfd is the only caller of alloc_fd this changing alloc_fd is trivially safe. Further this causes alloc_fd to take all of the same arguments as __alloc_fd except for the files_struct argument. Acked-by: Christian Brauner <christian.brauner@...ntu.com> v1: https://lkml.kernel.org/r/20200817220425.9389-15-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com> --- fs/file.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/file.c b/fs/file.c index 0d4ec0fa23b3..07e25f1b9dfd 100644 --- a/fs/file.c +++ b/fs/file.c @@ -538,9 +538,9 @@ int __alloc_fd(struct files_struct *files, return error; } -static int alloc_fd(unsigned start, unsigned flags) +static int alloc_fd(unsigned start, unsigned end, unsigned flags) { - return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); + return __alloc_fd(current->files, start, end, flags); } int __get_unused_fd_flags(unsigned flags, unsigned long nofile) @@ -1175,10 +1175,11 @@ SYSCALL_DEFINE1(dup, unsigned int, fildes) int f_dupfd(unsigned int from, struct file *file, unsigned flags) { + unsigned long nofile = rlimit(RLIMIT_NOFILE); int err; - if (from >= rlimit(RLIMIT_NOFILE)) + if (from >= nofile) return -EINVAL; - err = alloc_fd(from, flags); + err = alloc_fd(from, nofile, flags); if (err >= 0) { get_file(file); fd_install(err, file); -- 2.25.0
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