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b69edab47f
Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination
and source buffers. Defining kernel_headers_data as "char" would trip
this check. Since these addresses are treated as byte arrays, define
them as arrays (as done everywhere else).
This was seen with:
$ cat /sys/kernel/kheaders.tar.xz >> /dev/null
detected buffer overflow in memcpy
kernel BUG at lib/string_helpers.c:1027!
...
RIP: 0010:fortify_panic+0xf/0x20
[...]
Call Trace:
<TASK>
ikheaders_read+0x45/0x50 [kheaders]
kernfs_fop_read_iter+0x1a4/0x2f0
...
Reported-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20230302112130.6e402a98@kernel.org/
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Tested-by: Jakub Kicinski <kuba@kernel.org>
Fixes: 43d8ce9d65 ("Provide in-kernel headers to make extending kernel easier")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230302224946.never.243-kees@kernel.org
67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Provide kernel headers useful to build tracing programs
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* such as for running eBPF tracing tools.
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*
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* (Borrowed code from kernel/configs.c)
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/init.h>
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/*
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* Define kernel_headers_data and kernel_headers_data_end, within which the
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* compressed kernel headers are stored. The file is first compressed with xz.
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*/
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asm (
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" .pushsection .rodata, \"a\" \n"
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" .global kernel_headers_data \n"
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"kernel_headers_data: \n"
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" .incbin \"kernel/kheaders_data.tar.xz\" \n"
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" .global kernel_headers_data_end \n"
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"kernel_headers_data_end: \n"
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" .popsection \n"
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);
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extern char kernel_headers_data[];
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extern char kernel_headers_data_end[];
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static ssize_t
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ikheaders_read(struct file *file, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buf, loff_t off, size_t len)
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{
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memcpy(buf, &kernel_headers_data[off], len);
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return len;
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}
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static struct bin_attribute kheaders_attr __ro_after_init = {
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.attr = {
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.name = "kheaders.tar.xz",
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.mode = 0444,
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},
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.read = &ikheaders_read,
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};
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static int __init ikheaders_init(void)
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{
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kheaders_attr.size = (kernel_headers_data_end -
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kernel_headers_data);
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return sysfs_create_bin_file(kernel_kobj, &kheaders_attr);
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}
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static void __exit ikheaders_cleanup(void)
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{
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sysfs_remove_bin_file(kernel_kobj, &kheaders_attr);
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}
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module_init(ikheaders_init);
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module_exit(ikheaders_cleanup);
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR("Joel Fernandes");
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MODULE_DESCRIPTION("Echo the kernel header artifacts used to build the kernel");
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