On Thu, May 5, 2011 at 8:41 PM, <tim.gardner@xxxxxxxxxxxxx> wrote:
> From: Andy Whitcroft <apw@xxxxxxxxxxxxx>
>
> Currently there is no locking for updates to the registered_fb list.
> This allows an open through /dev/fbN to pick up a registered framebuffer
> pointer in parallel with it being released, as happens when a conflicting
> framebuffer is ejected or on module unload. There is also no reference
> counting on the framebuffer descriptor which is referenced from all open
> files, leading to references to released or reused memory to persist on
> these open files.
>
> This patch adds a reference count to the framebuffer descriptor to prevent
> it from being released until after all pending opens are closed. This
> allows the pending opens to detect the closed status and unmap themselves.
> It also adds locking to the framebuffer lookup path, locking it against
> the removal path such that it is possible to atomically lookup and take a
> reference to the descriptor. It also adds locking to the read and write
> paths which currently could access the framebuffer descriptor after it
> has been freed. Finally it moves the device to FBINFO_STATE_REMOVED to
> indicate that all access should be errored for this device.
>
> Signed-off-by: Andy Whitcroft <apw@xxxxxxxxxxxxx>
> Acked-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
> Signed-off-by: Leann Ogasawara <leann.ogasawara@xxxxxxxxxxxxx>
> Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
> ---
> drivers/video/fbmem.c | 132 ++++++++++++++++++++++++++++++++++++++-----------
> include/linux/fb.h | 2 +
> 2 files changed, 105 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
> index e0c2284..c8562c1 100644
> --- a/drivers/video/fbmem.c
> +++ b/drivers/video/fbmem.c
> @@ -42,6 +42,8 @@
>
> #define FBPIXMAPSIZE (1024 * 8)
>
> +/* Protects the registered framebuffer list and count. */
> +static DEFINE_SPINLOCK(registered_lock);
> struct fb_info *registered_fb[FB_MAX] __read_mostly;
> int num_registered_fb __read_mostly;
>
> @@ -694,9 +696,7 @@ static ssize_t
> fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> {
> unsigned long p = *ppos;
> - struct inode *inode = file->f_path.dentry->d_inode;
> - int fbidx = iminor(inode);
> - struct fb_info *info = registered_fb[fbidx];
> + struct fb_info *info = file->private_data;
> u8 *buffer, *dst;
> u8 __iomem *src;
> int c, cnt = 0, err = 0;
> @@ -705,19 +705,28 @@ fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> if (!info || ! info->screen_base)
> return -ENODEV;
>
> - if (info->state != FBINFO_STATE_RUNNING)
> - return -EPERM;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> +
> + if (info->state != FBINFO_STATE_RUNNING) {
> + err = -EPERM;
> + goto out_fb_info;
> + }
>
> - if (info->fbops->fb_read)
> - return info->fbops->fb_read(info, buf, count, ppos);
> + if (info->fbops->fb_read) {
> + err = info->fbops->fb_read(info, buf, count, ppos);
> + goto out_fb_info;
> + }
>
> total_size = info->screen_size;
>
> if (total_size == 0)
> total_size = info->fix.smem_len;
>
> - if (p >= total_size)
> - return 0;
> + if (p >= total_size) {
> + err = 0;
> + goto out_fb_info;
> + }
>
> if (count >= total_size)
> count = total_size;
> @@ -727,8 +736,10 @@ fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
>
> buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
> GFP_KERNEL);
> - if (!buffer)
> - return -ENOMEM;
> + if (!buffer) {
> + err = -ENOMEM;
> + goto out_fb_info;
> + }
>
> src = (u8 __iomem *) (info->screen_base + p);
>
> @@ -751,19 +762,21 @@ fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
> cnt += c;
> count -= c;
> }
> + if (!err)
> + err = cnt;
>
> kfree(buffer);
> +out_fb_info:
> + unlock_fb_info(info);
>
> - return (err) ? err : cnt;
> + return err;
> }
>
> static ssize_t
> fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
> {
> unsigned long p = *ppos;
> - struct inode *inode = file->f_path.dentry->d_inode;
> - int fbidx = iminor(inode);
> - struct fb_info *info = registered_fb[fbidx];
> + struct fb_info *info = file->private_data;
> u8 *buffer, *src;
> u8 __iomem *dst;
> int c, cnt = 0, err = 0;
> @@ -772,8 +785,13 @@ fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
> if (!info || !info->screen_base)
> return -ENODEV;
>
> - if (info->state != FBINFO_STATE_RUNNING)
> - return -EPERM;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> +
> + if (info->state != FBINFO_STATE_RUNNING) {
> + err = -EPERM;
> + goto out_fb_info;
> + }
>
> if (info->fbops->fb_write)
> return info->fbops->fb_write(info, buf, count, ppos);
> @@ -783,8 +801,10 @@ fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
> if (total_size == 0)
> total_size = info->fix.smem_len;
>
> - if (p > total_size)
> - return -EFBIG;
> + if (p > total_size) {
> + err = -EFBIG;
> + goto out_fb_info;
> + }
>
> if (count > total_size) {
> err = -EFBIG;
> @@ -800,8 +820,10 @@ fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
>
> buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
> GFP_KERNEL);
> - if (!buffer)
> - return -ENOMEM;
> + if (!buffer) {
> + err = -ENOMEM;
> + goto out_fb_info;
> + }
>
> dst = (u8 __iomem *) (info->screen_base + p);
>
> @@ -825,10 +847,14 @@ fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
> cnt += c;
> count -= c;
> }
> + if (cnt)
> + err = cnt;
>
> kfree(buffer);
> +out_fb_info:
> + unlock_fb_info(info);
>
> - return (cnt) ? cnt : err;
> + return err;
> }
>
> int
> @@ -1303,8 +1329,7 @@ static long fb_compat_ioctl(struct file *file, unsigned int cmd,
> static int
> fb_mmap(struct file *file, struct vm_area_struct * vma)
> {
> - int fbidx = iminor(file->f_path.dentry->d_inode);
> - struct fb_info *info = registered_fb[fbidx];
> + struct fb_info * const info = file->private_data;
> struct fb_ops *fb = info->fbops;
> unsigned long off;
> unsigned long start;
> @@ -1316,6 +1341,11 @@ fb_mmap(struct file *file, struct vm_area_struct * vma)
> if (!fb)
> return -ENODEV;
> mutex_lock(&info->mm_lock);
> + if (info->state == FBINFO_STATE_REMOVED) {
> + mutex_unlock(&info->mm_lock);
> + return -ENODEV;
> + }
> +
> if (fb->fb_mmap) {
> int res;
> res = fb->fb_mmap(info, vma);
> @@ -1352,6 +1382,34 @@ fb_mmap(struct file *file, struct vm_area_struct * vma)
> return 0;
> }
>
> +static struct fb_info *get_framebuffer_info(int idx)
> +__acquires(®istered_lock)
> +__releases(®istered_lock)
> +{
> + struct fb_info *fb_info;
> +
> + spin_lock(®istered_lock);
> + fb_info = registered_fb[idx];
> + fb_info->ref_count++;
> + spin_unlock(®istered_lock);
> +
> + return fb_info;
> +}
> +
> +static void put_framebuffer_info(struct fb_info *fb_info)
> +__acquires(®istered_lock)
> +__releases(®istered_lock)
> +{
> + int keep;
> +
> + spin_lock(®istered_lock);
> + keep = --fb_info->ref_count;
> + spin_unlock(®istered_lock);
> +
> + if (!keep && fb_info->fbops->fb_destroy)
> + fb_info->fbops->fb_destroy(fb_info);
> +}
> +
> static int
> fb_open(struct inode *inode, struct file *file)
> __acquires(&info->lock)
> @@ -1363,13 +1421,17 @@ __releases(&info->lock)
>
> if (fbidx >= FB_MAX)
> return -ENODEV;
> - info = registered_fb[fbidx];
> + info = get_framebuffer_info(fbidx);
> if (!info)
> request_module("fb%d", fbidx);
> - info = registered_fb[fbidx];
> + info = get_framebuffer_info(fbidx);
> if (!info)
> return -ENODEV;
> mutex_lock(&info->lock);
> + if (info->state == FBINFO_STATE_REMOVED) {
> + res = -ENODEV;
> + goto out;
> + }
> if (!try_module_get(info->fbops->owner)) {
> res = -ENODEV;
> goto out;
> @@ -1386,6 +1448,8 @@ __releases(&info->lock)
> #endif
> out:
> mutex_unlock(&info->lock);
> + if (res)
> + put_framebuffer_info(info);
> return res;
> }
>
> @@ -1401,6 +1465,7 @@ __releases(&info->lock)
> info->fbops->fb_release(info,1);
> module_put(info->fbops->owner);
> mutex_unlock(&info->lock);
> + put_framebuffer_info(info);
> return 0;
> }
>
> @@ -1549,6 +1614,7 @@ register_framebuffer(struct fb_info *fb_info)
> fb_info->node = i;
> mutex_init(&fb_info->lock);
> mutex_init(&fb_info->mm_lock);
> + fb_info->ref_count = 1;
>
> fb_info->dev = device_create(fb_class, fb_info->device,
> MKDEV(FB_MAJOR, i), NULL, "fb%d", i);
> @@ -1592,7 +1658,6 @@ register_framebuffer(struct fb_info *fb_info)
> return 0;
> }
>
> -
> /**
> * unregister_framebuffer - releases a frame buffer device
> * @fb_info: frame buffer info structure
> @@ -1627,6 +1692,16 @@ unregister_framebuffer(struct fb_info *fb_info)
> return -ENODEV;
> event.info = fb_info;
> ret = fb_notifier_call_chain(FB_EVENT_FB_UNBIND, &event);
> + if (!ret) {
> + mutex_lock(&fb_info->mm_lock);
> + /*
> + * We must prevent any operations for this transition, we
> + * already have info->lock so grab the info->mm_lock to hold
> + * the remainder.
> + */
> + fb_info->state = FBINFO_STATE_REMOVED;
> + mutex_unlock(&fb_info->mm_lock);
> + }
> unlock_fb_info(fb_info);
>
> if (ret) {
> @@ -1646,8 +1721,7 @@ unregister_framebuffer(struct fb_info *fb_info)
> fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
>
> /* this may free fb info */
> - if (fb_info->fbops->fb_destroy)
> - fb_info->fbops->fb_destroy(fb_info);
> + put_framebuffer_info(fb_info);
> done:
> return ret;
> }
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index df728c1..60de3fa 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -834,6 +834,7 @@ struct fb_tile_ops {
> struct fb_info {
> int node;
> int flags;
> + int ref_count;
> struct mutex lock; /* Lock for open/release/ioctl funcs */
> struct mutex mm_lock; /* Lock for fb_mmap and smem_* fields */
> struct fb_var_screeninfo var; /* Current var */
> @@ -873,6 +874,7 @@ struct fb_info {
> void *pseudo_palette; /* Fake palette of 16 colors */
> #define FBINFO_STATE_RUNNING 0
> #define FBINFO_STATE_SUSPENDED 1
> +#define FBINFO_STATE_REMOVED 2
> u32 state; /* Hardware state i.e suspend */
> void *fbcon_par; /* fbcon use-only private area */
> /* From here on everything is device dependent */
> --
> 1.7.0.4
>
> --
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> Please read the FAQ at http://www.tux.org/lkml/
>
Tested-by: Anca Emanuel <anca.emanuel.gmail.com>
I can not use S3 resume without this.
[ 21.964367] BUG: unable to handle kernel paging request at 0000010a00000010
[ 21.964396] IP: [<ffffffff8130abe0>] fb_release+0x30/0x70
[ 21.964410] PGD 0
[ 21.964416] Oops: 0000 [#1] SMP
[ 21.964424] last sysfs file: /sys/devices/virtual/vtconsole/vtcon1/uevent
[ 21.964434] CPU 1
[ 21.964438] Modules linked in: parport_pc ppdev
snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm
adt7475 hwmon_vid snd_seq_midi snd_rawmidi snd_seq_midi_event nouveau
snd_seq snd_timer snd_seq_device ttm drm_kms_helper snd intel_agp
psmouse soundcore serio_raw intel_gtt snd_page_alloc drm i2c_algo_bit
video lp parport pata_marvell ahci libahci r8169 mii
[ 21.964528]
[ 21.964533] Pid: 221, comm: plymouthd Not tainted 2.6.39-rc6 #7
MICRO-STAR INTERNATIONAL CO.,LTD MS-7360/MS-7360
[ 21.964548] RIP: 0010:[<ffffffff8130abe0>] [<ffffffff8130abe0>]
fb_release+0x30/0x70
[ 21.964560] RSP: 0018:ffff880037211eb8 EFLAGS: 00010286
[ 21.964566] RAX: ffff880037210000 RBX: ffff88007f817000 RCX: 0000000000000001
[ 21.964573] RDX: 0000010a00000000 RSI: ffff8800370f5540 RDI: ffff88007f817008
[ 21.964580] RBP: ffff880037211ec8 R08: 0000000000000000 R09: 0000000000000000
[ 21.964588] R10: ffff8800370f5550 R11: 0000000000000246 R12: ffff88007f817008
[ 21.964595] R13: ffff88007d3db540 R14: ffff88007be34d90 R15: ffff88007be34d90
[ 21.964604] FS: 00007fb335025720(0000) GS:ffff88007fc80000(0000)
knlGS:0000000000000000
[ 21.964739] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 21.964746] CR2: 0000010a00000010 CR3: 000000007b41a000 CR4: 00000000000006e0
[ 21.964754] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 21.964762] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 21.964770] Process plymouthd (pid: 221, threadinfo
ffff880037210000, task ffff880036cd16c0)
[ 21.964778] Stack:
[ 21.964782] ffff8800370f5540 0000000000000008 ffff880037211f18
ffffffff8115cfaa
[ 21.964797] ffff8800370f5550 ffff8800793c7b00 ffff88006744fcd0
ffff8800370f5540
[ 21.964811] ffff88007c3b9080 0000000000000000 000000000000000b
0000000000000000
[ 21.964825] Call Trace:
[ 21.964834] [<ffffffff8115cfaa>] fput+0xea/0x220
[ 21.964842] [<ffffffff811591f6>] filp_close+0x66/0x90
[ 21.964849] [<ffffffff811597c7>] sys_close+0xb7/0x120
[ 21.964858] [<ffffffff815b3002>] system_call_fastpath+0x16/0x1b
[ 21.964865] Code: 83 ec 10 48 89 1c 24 4c 89 64 24 08 0f 1f 44 00
00 48 8b 9e a0 00 00 00 4c 8d 63 08 4c 89 e7 e8 d7 ea 29 00 48 8b 93
b8 03 00 00
[ 21.964944] 8b 42 10 48 85 c0 74 11 be 01 00 00 00 48 89 df ff d0 48 8b
[ 21.964983] RIP [<ffffffff8130abe0>] fb_release+0x30/0x70
[ 21.964992] RSP <ffff880037211eb8>
[ 21.964997] CR2: 0000010a00000010
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