Commit e06b53c2 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

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: default avatarChristian Brauner <christian.brauner@ubuntu.com>
v1: https://lkml.kernel.org/r/20200817220425.9389-15-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20201120231441.29911-19-ebiederm@xmission.com


Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent d74ba04d

fs/file.c

+5 −4
Original line number Diff line number Diff line
@@ -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);