lockdown: Lock down /proc/kcore

Disallow access to /proc/kcore when the kernel is locked down to prevent access to cryptographic data. This is limited to lockdown confidentiality mode and is still permitted in integrity mode. Signed-off-by: David Howells <[email protected]> Signed-off-by: Matthew Garrett <[email protected]> Reviewed-by: Kees Cook <[email protected]> Signed-off-by: James Morris <[email protected]>
Pankaj161982 · Aug 20, 2019 · 02e935b · 02e935b
1 parent 906357f
commit 02e935b
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diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
@@ -31,6 +31,7 @@
 #include <linux/ioport.h>
 #include <linux/memory.h>
 #include <linux/sched/task.h>
+#include <linux/security.h>
 #include <asm/sections.h>
 #include "internal.h"
 
@@ -545,6 +546,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 
 static int open_kcore(struct inode *inode, struct file *filp)
 {
+	int ret = security_locked_down(LOCKDOWN_KCORE);
+
+	if (ret)
+		return ret;
 	if (!capable(CAP_SYS_RAWIO))
 		return -EPERM;
 

diff --git a/include/linux/security.h b/include/linux/security.h
@@ -116,6 +116,7 @@ enum lockdown_reason {
 	LOCKDOWN_MODULE_PARAMETERS,
 	LOCKDOWN_MMIOTRACE,
 	LOCKDOWN_INTEGRITY_MAX,
+	LOCKDOWN_KCORE,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
 

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
@@ -31,6 +31,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters",
 	[LOCKDOWN_MMIOTRACE] = "unsafe mmio",
 	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
+	[LOCKDOWN_KCORE] = "/proc/kcore access",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };