On 10/30/20 3:08 AM, Daniel Vetter wrote:
We want all iomem mmaps to consistently revoke ptes when the kernel
takes over and CONFIG_IO_STRICT_DEVMEM is enabled. This includes the
pci bar mmaps available through procfs and sysfs, which currently do
not revoke mappings.
To prepare for this, move the code from the /dev/kmem driver to
kernel/resource.c.
This seems like it's doing a lot more than just code movement, right?
Should we list some of that here?
Also, I'm seeing a crash due to this commit. More below:
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-samsung-soc@xxxxxxxxxxxxxxx
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
--
v3:
- add barrier for consistency and document why we don't have to check
for NULL (Jason)
v4
- Adjust comments to reflect the general nature of this iomem revoke
code now (Dan)
---
drivers/char/mem.c | 85 +---------------------------------
include/linux/ioport.h | 6 +--
kernel/resource.c | 101 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 102 insertions(+), 90 deletions(-)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 7dcf9e4ea79d..43c871dc7477 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -31,9 +31,6 @@
#include <linux/uio.h>
#include <linux/uaccess.h>
#include <linux/security.h>
-#include <linux/pseudo_fs.h>
-#include <uapi/linux/magic.h>
-#include <linux/mount.h>
#ifdef CONFIG_IA64
# include <linux/efi.h>
@@ -836,42 +833,6 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
return ret;
}
-static struct inode *devmem_inode;
-
-#ifdef CONFIG_IO_STRICT_DEVMEM
-void revoke_devmem(struct resource *res)
-{
- /* pairs with smp_store_release() in devmem_init_inode() */
- struct inode *inode = smp_load_acquire(&devmem_inode);
-
- /*
- * Check that the initialization has completed. Losing the race
- * is ok because it means drivers are claiming resources before
- * the fs_initcall level of init and prevent /dev/mem from
- * establishing mappings.
- */
- if (!inode)
- return;
-
- /*
- * The expectation is that the driver has successfully marked
- * the resource busy by this point, so devmem_is_allowed()
- * should start returning false, however for performance this
- * does not iterate the entire resource range.
- */
- if (devmem_is_allowed(PHYS_PFN(res->start)) &&
- devmem_is_allowed(PHYS_PFN(res->end))) {
- /*
- * *cringe* iomem=relaxed says "go ahead, what's the
- * worst that can happen?"
- */
- return;
- }
-
- unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
-}
-#endif
-
static int open_port(struct inode *inode, struct file *filp)
{
int rc;
@@ -891,7 +852,7 @@ static int open_port(struct inode *inode, struct file *filp)
* revocations when drivers want to take over a /dev/mem mapped
* range.
*/
- filp->f_mapping = inode->i_mapping;
+ filp->f_mapping = iomem_get_mapping();
The problem is that iomem_get_mapping() returns NULL for the !CONFIG_IO_STRICT_DEVMEM
case. And then we have pre-existing fs code that expects to go "up and over", like this:
static int do_dentry_open(struct file *f,
struct inode *inode,
int (*open)(struct inode *, struct file *))
{
...
file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
...and it crashes on that line fairly early in bootup.
Not sure what to suggest for this patch, but wanted to get this report out at least.
thanks,
--
John Hubbard
NVIDIA
return 0;
}
@@ -1023,48 +984,6 @@ static char *mem_devnode(struct device *dev, umode_t *mode)
static struct class *mem_class;
-static int devmem_fs_init_fs_context(struct fs_context *fc)
-{
- return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type devmem_fs_type = {
- .name = "devmem",
- .owner = THIS_MODULE,
- .init_fs_context = devmem_fs_init_fs_context,
- .kill_sb = kill_anon_super,
-};
-
-static int devmem_init_inode(void)
-{
- static struct vfsmount *devmem_vfs_mount;
- static int devmem_fs_cnt;
- struct inode *inode;
- int rc;
-
- rc = simple_pin_fs(&devmem_fs_type, &devmem_vfs_mount, &devmem_fs_cnt);
- if (rc < 0) {
- pr_err("Cannot mount /dev/mem pseudo filesystem: %d\n", rc);
- return rc;
- }
-
- inode = alloc_anon_inode(devmem_vfs_mount->mnt_sb);
- if (IS_ERR(inode)) {
- rc = PTR_ERR(inode);
- pr_err("Cannot allocate inode for /dev/mem: %d\n", rc);
- simple_release_fs(&devmem_vfs_mount, &devmem_fs_cnt);
- return rc;
- }
-
- /*
- * Publish /dev/mem initialized.
- * Pairs with smp_load_acquire() in revoke_devmem().
- */
- smp_store_release(&devmem_inode, inode);
-
- return 0;
-}
-
static int __init chr_dev_init(void)
{
int minor;
@@ -1086,8 +1005,6 @@ static int __init chr_dev_init(void)
*/
if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
continue;
- if ((minor == DEVMEM_MINOR) && devmem_init_inode() != 0)
- continue;
device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
NULL, devlist[minor].name);
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 5135d4b86cd6..02a5466245c0 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -307,11 +307,7 @@ struct resource *devm_request_free_mem_region(struct device *dev,
struct resource *request_free_mem_region(struct resource *base,
unsigned long size, const char *name);
-#ifdef CONFIG_IO_STRICT_DEVMEM
-void revoke_devmem(struct resource *res);
-#else
-static inline void revoke_devmem(struct resource *res) { };
-#endif
+extern struct address_space *iomem_get_mapping(void);
#endif /* __ASSEMBLY__ */
#endif /* _LINUX_IOPORT_H */
diff --git a/kernel/resource.c b/kernel/resource.c
index 3ae2f56cc79d..5ecc3187fe2d 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -18,12 +18,15 @@
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
+#include <linux/pseudo_fs.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/pfn.h>
#include <linux/mm.h>
+#include <linux/mount.h>
#include <linux/resource_ext.h>
+#include <uapi/linux/magic.h>
#include <asm/io.h>
@@ -1115,6 +1118,58 @@ resource_size_t resource_alignment(struct resource *res)
static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
+static struct inode *iomem_inode;
+
+#ifdef CONFIG_IO_STRICT_DEVMEM
+static void revoke_iomem(struct resource *res)
+{
+ /* pairs with smp_store_release() in iomem_init_inode() */
+ struct inode *inode = smp_load_acquire(&iomem_inode);
+
+ /*
+ * Check that the initialization has completed. Losing the race
+ * is ok because it means drivers are claiming resources before
+ * the fs_initcall level of init and prevent iomem_get_mapping users
+ * from establishing mappings.
+ */
+ if (!inode)
+ return;
+
+ /*
+ * The expectation is that the driver has successfully marked
+ * the resource busy by this point, so devmem_is_allowed()
+ * should start returning false, however for performance this
+ * does not iterate the entire resource range.
+ */
+ if (devmem_is_allowed(PHYS_PFN(res->start)) &&
+ devmem_is_allowed(PHYS_PFN(res->end))) {
+ /*
+ * *cringe* iomem=relaxed says "go ahead, what's the
+ * worst that can happen?"
+ */
+ return;
+ }
+
+ unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
+}
+struct address_space *iomem_get_mapping(void)
+{
+ /*
+ * This function is only called from file open paths, hence guaranteed
+ * that fs_initcalls have completed and no need to check for NULL. But
+ * since revoke_iomem can be called before the initcall we still need
+ * the barrier to appease checkers.
+ */
+ return smp_load_acquire(&iomem_inode)->i_mapping;
+}
+#else
+static void revoke_iomem(struct resource *res) {}
+struct address_space *iomem_get_mapping(void)
+{
+ return NULL;
+}
+#endif
+
/**
* __request_region - create a new busy resource region
* @parent: parent resource descriptor
@@ -1182,7 +1237,7 @@ struct resource * __request_region(struct resource *parent,
write_unlock(&resource_lock);
if (res && orig_parent == &iomem_resource)
- revoke_devmem(res);
+ revoke_iomem(res);
return res;
}
@@ -1782,4 +1837,48 @@ static int __init strict_iomem(char *str)
return 1;
}
+static int iomem_fs_init_fs_context(struct fs_context *fc)
+{
+ return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
+}
+
+static struct file_system_type iomem_fs_type = {
+ .name = "iomem",
+ .owner = THIS_MODULE,
+ .init_fs_context = iomem_fs_init_fs_context,
+ .kill_sb = kill_anon_super,
+};
+
+static int __init iomem_init_inode(void)
+{
+ static struct vfsmount *iomem_vfs_mount;
+ static int iomem_fs_cnt;
+ struct inode *inode;
+ int rc;
+
+ rc = simple_pin_fs(&iomem_fs_type, &iomem_vfs_mount, &iomem_fs_cnt);
+ if (rc < 0) {
+ pr_err("Cannot mount iomem pseudo filesystem: %d\n", rc);
+ return rc;
+ }
+
+ inode = alloc_anon_inode(iomem_vfs_mount->mnt_sb);
+ if (IS_ERR(inode)) {
+ rc = PTR_ERR(inode);
+ pr_err("Cannot allocate inode for iomem: %d\n", rc);
+ simple_release_fs(&iomem_vfs_mount, &iomem_fs_cnt);
+ return rc;
+ }
+
+ /*
+ * Publish iomem revocation inode initialized.
+ * Pairs with smp_load_acquire() in revoke_iomem().
+ */
+ smp_store_release(&iomem_inode, inode);
+
+ return 0;
+}
+
+fs_initcall(iomem_init_inode);
+
__setup("iomem=", strict_iomem);
