Messages in this thread | | | Date | Wed, 4 May 2022 11:27:10 +0200 | Subject | Re: [PATCH v2] fbdev: Use helper to get fb_info in all file operations | From | Thomas Zimmermann <> |
| |
Hi
Am 04.05.22 um 11:02 schrieb Daniel Vetter: > On Tue, May 03, 2022 at 10:19:34PM +0200, Javier Martinez Canillas wrote: >> A reference to the framebuffer device struct fb_info is stored in the file >> private data, but this reference could no longer be valid and must not be >> accessed directly. Instead, the file_fb_info() accessor function must be >> used since it does sanity checking to make sure that the fb_info is valid. >> >> This can happen for example if the registered framebuffer device is for a >> driver that just uses a framebuffer provided by the system firmware. In >> that case, the fbdev core would unregister the framebuffer device when a >> real video driver is probed and ask to remove conflicting framebuffers. >> >> Most fbdev file operations already use the helper to get the fb_info but >> get_fb_unmapped_area() and fb_deferred_io_fsync() don't. Fix those two. >> >> Since fb_deferred_io_fsync() is not in fbmem.o, the helper has to be >> exported. Rename it and add a fb_ prefix to denote that is public now. >> >> Reported-by: Junxiao Chang <junxiao.chang@intel.com> >> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > > Note that fb_file_info is hilariously racy since there's nothing > preventing a concurrenct framebuffer_unregister. Or at least I'm not > seeing anything. See cf4a3ae4ef33 ("fbdev: lock_fb_info cannot fail") for > context, maybe reference that commit here in your patch.
Can we acquire registration_lock around [1]?
[1] https://elixir.bootlin.com/linux/v5.17.5/source/drivers/video/fbdev/core/fbmem.c#L756
> > Either way this doesn't really make anything worse, so > Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > Cheers, Daniel > >> --- >> >> Changes in v2: >> - Fix copy & paste error passing file->private_data instead of file >> to fb_file_fb_info() function (Sam Ravnborg). >> >> drivers/video/fbdev/core/fb_defio.c | 5 ++++- >> drivers/video/fbdev/core/fbmem.c | 24 +++++++++++++++--------- >> include/linux/fb.h | 1 + >> 3 files changed, 20 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c >> index 842c66b3e33d..ccdf903c48bd 100644 >> --- a/drivers/video/fbdev/core/fb_defio.c >> +++ b/drivers/video/fbdev/core/fb_defio.c >> @@ -68,12 +68,15 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf) >> >> int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasync) >> { >> - struct fb_info *info = file->private_data; >> + struct fb_info *info = fb_file_fb_info(file); >> struct inode *inode = file_inode(file); >> int err = file_write_and_wait_range(file, start, end); >> if (err) >> return err; >> >> + if (!info) >> + return -ENODEV; >> + >> /* Skip if deferred io is compiled-in but disabled on this fbdev */ >> if (!info->fbdefio) >> return 0; >> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c >> index 97eb0dee411c..ba2c14a1087d 100644 >> --- a/drivers/video/fbdev/core/fbmem.c >> +++ b/drivers/video/fbdev/core/fbmem.c >> @@ -745,7 +745,7 @@ static const struct seq_operations __maybe_unused proc_fb_seq_ops = { >> * So look up the fb_info using the inode minor number, >> * and just verify it against the reference we have. >> */ >> -static struct fb_info *file_fb_info(struct file *file) >> +struct fb_info *fb_file_fb_info(struct file *file) >> { >> struct inode *inode = file_inode(file); >> int fbidx = iminor(inode); >> @@ -755,12 +755,13 @@ static struct fb_info *file_fb_info(struct file *file) >> info = NULL; >> return info; >> } >> +EXPORT_SYMBOL(fb_file_fb_info); >> >> static ssize_t >> fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) >> { >> unsigned long p = *ppos; >> - struct fb_info *info = file_fb_info(file); >> + struct fb_info *info = fb_file_fb_info(file); >> u8 *buffer, *dst; >> u8 __iomem *src; >> int c, cnt = 0, err = 0; >> @@ -825,7 +826,7 @@ static ssize_t >> fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) >> { >> unsigned long p = *ppos; >> - struct fb_info *info = file_fb_info(file); >> + struct fb_info *info = fb_file_fb_info(file); >> u8 *buffer, *src; >> u8 __iomem *dst; >> int c, cnt = 0, err = 0; >> @@ -1181,7 +1182,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, >> >> static long fb_ioctl(struct file *file, unsigned int cmd, unsigned long arg) >> { >> - struct fb_info *info = file_fb_info(file); >> + struct fb_info *info = fb_file_fb_info(file); >> >> if (!info) >> return -ENODEV; >> @@ -1293,7 +1294,7 @@ static int fb_get_fscreeninfo(struct fb_info *info, unsigned int cmd, >> static long fb_compat_ioctl(struct file *file, unsigned int cmd, >> unsigned long arg) >> { >> - struct fb_info *info = file_fb_info(file); >> + struct fb_info *info = fb_file_fb_info(file); >> const struct fb_ops *fb; >> long ret = -ENOIOCTLCMD; >> >> @@ -1333,7 +1334,7 @@ static long fb_compat_ioctl(struct file *file, unsigned int cmd, >> static int >> fb_mmap(struct file *file, struct vm_area_struct * vma) >> { >> - struct fb_info *info = file_fb_info(file); >> + struct fb_info *info = fb_file_fb_info(file); >> int (*fb_mmap_fn)(struct fb_info *info, struct vm_area_struct *vma); >> unsigned long mmio_pgoff; >> unsigned long start; >> @@ -1434,7 +1435,7 @@ fb_release(struct inode *inode, struct file *file) >> __acquires(&info->lock) >> __releases(&info->lock) >> { >> - struct fb_info * const info = file_fb_info(file); >> + struct fb_info * const info = fb_file_fb_info(file); >> >> if (!info) >> return -ENODEV; >> @@ -1453,8 +1454,13 @@ unsigned long get_fb_unmapped_area(struct file *filp, >> unsigned long addr, unsigned long len, >> unsigned long pgoff, unsigned long flags) >> { >> - struct fb_info * const info = filp->private_data; >> - unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len); >> + struct fb_info * const info = fb_file_fb_info(filp); >> + unsigned long fb_size; >> + >> + if (!info) >> + return -ENODEV; >> + >> + fb_size = PAGE_ALIGN(info->fix.smem_len); >> >> if (pgoff > fb_size || len > fb_size - pgoff) >> return -EINVAL; >> diff --git a/include/linux/fb.h b/include/linux/fb.h >> index 9a77ab615c36..3004b8b8c5c2 100644 >> --- a/include/linux/fb.h >> +++ b/include/linux/fb.h >> @@ -624,6 +624,7 @@ extern int fb_get_color_depth(struct fb_var_screeninfo *var, >> struct fb_fix_screeninfo *fix); >> extern int fb_get_options(const char *name, char **option); >> extern int fb_new_modelist(struct fb_info *info); >> +extern struct fb_info *fb_file_fb_info(struct file *file); >> >> extern struct fb_info *registered_fb[FB_MAX]; >> extern int num_registered_fb; >> -- >> 2.35.1 >> >
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev [unhandled content-type:application/pgp-signature] | |