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authorArjan van de Ven <arjan@linux.intel.com>2008-04-24 23:40:47 +0200
committerIngo Molnar <mingo@elte.hu>2008-04-24 23:40:47 +0200
commitae531c26c5c2a28ca1b35a75b39b3b256850f2c8 (patch)
treee4c2f3ec25bdb0e2e5f7f15f79a60c3175f03718 /drivers
parent94bc891b00e40cbec375feb4568780af183fd7f4 (diff)
x86: introduce /dev/mem restrictions with a config option
This patch introduces a restriction on /dev/mem: Only non-memory can be read or written unless the newly introduced config option is set. The X server needs access to /dev/mem for the PCI space, but it doesn't need access to memory; both the file permissions and SELinux permissions of /dev/mem just make X effectively super-super powerful. With the exception of the BIOS area, there's just no valid app that uses /dev/mem on actual memory. Other popular users of /dev/mem are rootkits and the like. (note: mmap access of memory via /dev/mem was already not allowed since a really long time) People who want to use /dev/mem for kernel debugging can enable the config option. The restrictions of this patch have been in the Fedora and RHEL kernels for at least 4 years without any problems. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/char/mem.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 20070b7c573..dcf6e31970a 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -108,6 +108,30 @@ static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
}
#endif
+#ifdef CONFIG_NONPROMISC_DEVMEM
+static inline int range_is_allowed(unsigned long from, unsigned long to)
+{
+ unsigned long cursor;
+
+ cursor = from >> PAGE_SHIFT;
+ while ((cursor << PAGE_SHIFT) < to) {
+ if (!devmem_is_allowed(cursor)) {
+ printk(KERN_INFO "Program %s tried to read /dev/mem "
+ "between %lx->%lx.\n",
+ current->comm, from, to);
+ return 0;
+ }
+ cursor++;
+ }
+ return 1;
+}
+#else
+static inline int range_is_allowed(unsigned long from, unsigned long to)
+{
+ return 1;
+}
+#endif
+
/*
* This funcion reads the *physical* memory. The f_pos points directly to the
* memory location.
@@ -157,6 +181,8 @@ static ssize_t read_mem(struct file * file, char __user * buf,
*/
ptr = xlate_dev_mem_ptr(p);
+ if (!range_is_allowed(p, p+count))
+ return -EPERM;
if (copy_to_user(buf, ptr, sz))
return -EFAULT;
buf += sz;
@@ -214,6 +240,8 @@ static ssize_t write_mem(struct file * file, const char __user * buf,
*/
ptr = xlate_dev_mem_ptr(p);
+ if (!range_is_allowed(p, p+sz))
+ return -EPERM;
copied = copy_from_user(ptr, buf, sz);
if (copied) {
written += sz - copied;