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Revision ec057595cb3fb339e692898bedccd566160ba086 authored by Linus Torvalds on 06 December 2019, 20:40:35 UTC, committed by Linus Torvalds on 06 December 2019, 20:40:35 UTC 
pipe: fix incorrect caching of pipe state over pipe_wait()
 
Similarly to commit 8f868d68d335 ("pipe: Fix missing mask update after
pipe_wait()") this fixes a case where the pipe rewrite ended up caching
the pipe state incorrectly over a pipe lock drop event.

It wasn't quite as obvious, because you needed to splice data from a
pipe to a file, which is a fairly unusual operation, but it's completely
wrong.

Make sure we load the pipe head/tail/size information only after we've
waited for there to be data in the pipe.

While in that file, also make one of the splice helper functions use the
canonical arghument order for pipe_empty().  That's syntactic - pipe
emptiness is just that head and tail are equal, and thus mixing up head
and tail doesn't really matter.  It's still wrong, though.

Reported-by: David Sterba <dsterba@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 7ada90e
Raw File
kheaders.c 
// SPDX-License-Identifier: GPL-2.0
/*
 * Provide kernel headers useful to build tracing programs
 * such as for running eBPF tracing tools.
 *
 * (Borrowed code from kernel/configs.c)
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/init.h>

/*
 * Define kernel_headers_data and kernel_headers_data_end, within which the
 * compressed kernel headers are stored. The file is first compressed with xz.
 */

asm (
"	.pushsection .rodata, \"a\"		\n"
"	.global kernel_headers_data		\n"
"kernel_headers_data:				\n"
"	.incbin \"kernel/kheaders_data.tar.xz\"	\n"
"	.global kernel_headers_data_end		\n"
"kernel_headers_data_end:			\n"
"	.popsection				\n"
);

extern char kernel_headers_data;
extern char kernel_headers_data_end;

static ssize_t
ikheaders_read(struct file *file,  struct kobject *kobj,
	       struct bin_attribute *bin_attr,
	       char *buf, loff_t off, size_t len)
{
	memcpy(buf, &kernel_headers_data + off, len);
	return len;
}

static struct bin_attribute kheaders_attr __ro_after_init = {
	.attr = {
		.name = "kheaders.tar.xz",
		.mode = 0444,
	},
	.read = &ikheaders_read,
};

static int __init ikheaders_init(void)
{
	kheaders_attr.size = (&kernel_headers_data_end -
			      &kernel_headers_data);
	return sysfs_create_bin_file(kernel_kobj, &kheaders_attr);
}

static void __exit ikheaders_cleanup(void)
{
	sysfs_remove_bin_file(kernel_kobj, &kheaders_attr);
}

module_init(ikheaders_init);
module_exit(ikheaders_cleanup);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Joel Fernandes");
MODULE_DESCRIPTION("Echo the kernel header artifacts used to build the kernel");
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