| Message ID | 20201030100815.2269-14-daniel.vetter@ffwll.ch |
|---|---|
| State | Superseded |
| Headers | show |
| Series | follow_pfn and other iomap races | expand |
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@linuxfoundation.org> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > Cc: Jason Gunthorpe <jgg@ziepe.ca> > Cc: Kees Cook <keescook@chromium.org> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: John Hubbard <jhubbard@nvidia.com> > Cc: Jérôme Glisse <jglisse@redhat.com> > Cc: Jan Kara <jack@suse.cz> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: linux-mm@kvack.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-samsung-soc@vger.kernel.org > Cc: linux-media@vger.kernel.org > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: David Hildenbrand <david@redhat.com> > Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> > -- > 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); >
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(); 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);