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fbmem: don't call copy_from/to_user() with mutex held
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Avoid calling copy_from/to_user() with fb_info->lock mutex held in fbmem
ioctl().

fb_mmap() is called under mm->mmap_sem (A) held, that also acquires
fb_info->lock (B); fb_ioctl() takes fb_info->lock (B) and does
copy_from/to_user() that might acquire mm->mmap_sem (A), causing a
deadlock.

NOTE: it doesn't push down the fb_info->lock in each own driver's
fb_ioctl(), so there are still potential deadlocks elsewhere.

Signed-off-by: Andrea Righi <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Krzysztof Helt <[email protected]>
Cc: Harvey Harrison <[email protected]>
Cc: Stefan Richter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@arighi @torvalds
arighi authored and torvalds committed Feb 5, 2009
1 parent afd8d0f commit 1f5e31d
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Showing 3 changed files with 98 additions and 72 deletions.
20 changes: 14 additions & 6 deletions drivers/video/fbcmap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -250,10 +250,6 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *info)
int rc, size = cmap->len * sizeof(u16);
struct fb_cmap umap;

if (cmap->start < 0 || (!info->fbops->fb_setcolreg &&
!info->fbops->fb_setcmap))
return -EINVAL;

memset(&umap, 0, sizeof(struct fb_cmap));
rc = fb_alloc_cmap(&umap, cmap->len, cmap->transp != NULL);
if (rc)
Expand All @@ -262,11 +258,23 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *info)
copy_from_user(umap.green, cmap->green, size) ||
copy_from_user(umap.blue, cmap->blue, size) ||
(cmap->transp && copy_from_user(umap.transp, cmap->transp, size))) {
fb_dealloc_cmap(&umap);
return -EFAULT;
rc = -EFAULT;
goto out;
}
umap.start = cmap->start;
if (!lock_fb_info(info)) {
rc = -ENODEV;
goto out;
}
if (cmap->start < 0 || (!info->fbops->fb_setcolreg &&
!info->fbops->fb_setcmap)) {
rc = -EINVAL;
goto out1;
}
rc = fb_set_cmap(&umap, info);
out1:
unlock_fb_info(info);
out:
fb_dealloc_cmap(&umap);
return rc;
}
Expand Down
135 changes: 69 additions & 66 deletions drivers/video/fbmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1013,132 +1013,139 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
struct fb_var_screeninfo var;
struct fb_fix_screeninfo fix;
struct fb_con2fbmap con2fb;
struct fb_cmap cmap_from;
struct fb_cmap_user cmap;
struct fb_event event;
void __user *argp = (void __user *)arg;
long ret = 0;

fb = info->fbops;
if (!fb)
return -ENODEV;

switch (cmd) {
case FBIOGET_VSCREENINFO:
ret = copy_to_user(argp, &info->var,
sizeof(var)) ? -EFAULT : 0;
if (!lock_fb_info(info))
return -ENODEV;
var = info->var;
unlock_fb_info(info);

ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0;
break;
case FBIOPUT_VSCREENINFO:
if (copy_from_user(&var, argp, sizeof(var))) {
ret = -EFAULT;
break;
}
if (copy_from_user(&var, argp, sizeof(var)))
return -EFAULT;
if (!lock_fb_info(info))
return -ENODEV;
acquire_console_sem();
info->flags |= FBINFO_MISC_USEREVENT;
ret = fb_set_var(info, &var);
info->flags &= ~FBINFO_MISC_USEREVENT;
release_console_sem();
if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
unlock_fb_info(info);
if (!ret && copy_to_user(argp, &var, sizeof(var)))
ret = -EFAULT;
break;
case FBIOGET_FSCREENINFO:
ret = copy_to_user(argp, &info->fix,
sizeof(fix)) ? -EFAULT : 0;
if (!lock_fb_info(info))
return -ENODEV;
fix = info->fix;
unlock_fb_info(info);

ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0;
break;
case FBIOPUTCMAP:
if (copy_from_user(&cmap, argp, sizeof(cmap)))
ret = -EFAULT;
else
ret = fb_set_user_cmap(&cmap, info);
return -EFAULT;
ret = fb_set_user_cmap(&cmap, info);
break;
case FBIOGETCMAP:
if (copy_from_user(&cmap, argp, sizeof(cmap)))
ret = -EFAULT;
else
ret = fb_cmap_to_user(&info->cmap, &cmap);
return -EFAULT;
if (!lock_fb_info(info))
return -ENODEV;
cmap_from = info->cmap;
unlock_fb_info(info);
ret = fb_cmap_to_user(&cmap_from, &cmap);
break;
case FBIOPAN_DISPLAY:
if (copy_from_user(&var, argp, sizeof(var))) {
ret = -EFAULT;
break;
}
if (copy_from_user(&var, argp, sizeof(var)))
return -EFAULT;
if (!lock_fb_info(info))
return -ENODEV;
acquire_console_sem();
ret = fb_pan_display(info, &var);
release_console_sem();
unlock_fb_info(info);
if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
ret = -EFAULT;
return -EFAULT;
break;
case FBIO_CURSOR:
ret = -EINVAL;
break;
case FBIOGET_CON2FBMAP:
if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
ret = -EFAULT;
else if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
ret = -EINVAL;
else {
con2fb.framebuffer = -1;
event.info = info;
event.data = &con2fb;
fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP,
&event);
ret = copy_to_user(argp, &con2fb,
sizeof(con2fb)) ? -EFAULT : 0;
}
return -EFAULT;
if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
return -EINVAL;
con2fb.framebuffer = -1;
event.data = &con2fb;

if (!lock_fb_info(info))
return -ENODEV;
event.info = info;
fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event);
unlock_fb_info(info);

ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0;
break;
case FBIOPUT_CON2FBMAP:
if (copy_from_user(&con2fb, argp, sizeof(con2fb))) {
ret = -EFAULT;
break;
}
if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES) {
ret = -EINVAL;
break;
}
if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX) {
ret = -EINVAL;
break;
}
if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
return -EFAULT;
if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
return -EINVAL;
if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)
return -EINVAL;
if (!registered_fb[con2fb.framebuffer])
request_module("fb%d", con2fb.framebuffer);
if (!registered_fb[con2fb.framebuffer]) {
ret = -EINVAL;
break;
}
event.info = info;
event.data = &con2fb;
if (!lock_fb_info(info))
return -ENODEV;
event.info = info;
ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP,
&event);
unlock_fb_info(info);
break;
case FBIOBLANK:
if (!lock_fb_info(info))
return -ENODEV;
acquire_console_sem();
info->flags |= FBINFO_MISC_USEREVENT;
ret = fb_blank(info, arg);
info->flags &= ~FBINFO_MISC_USEREVENT;
release_console_sem();
break;;
unlock_fb_info(info);
break;
default:
if (fb->fb_ioctl == NULL)
ret = -ENOTTY;
else
if (!lock_fb_info(info))
return -ENODEV;
fb = info->fbops;
if (fb->fb_ioctl)
ret = fb->fb_ioctl(info, cmd, arg);
else
ret = -ENOTTY;
unlock_fb_info(info);
}
return ret;
}

static long fb_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
__acquires(&info->lock)
__releases(&info->lock)
{
struct inode *inode = file->f_path.dentry->d_inode;
int fbidx = iminor(inode);
struct fb_info *info;
long ret;
struct fb_info *info = registered_fb[fbidx];

info = registered_fb[fbidx];
mutex_lock(&info->lock);
ret = do_fb_ioctl(info, cmd, arg);
mutex_unlock(&info->lock);
return ret;
return do_fb_ioctl(info, cmd, arg);
}

#ifdef CONFIG_COMPAT
Expand Down Expand Up @@ -1257,16 +1264,13 @@ 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)
__acquires(&info->lock)
__releases(&info->lock)
{
struct inode *inode = file->f_path.dentry->d_inode;
int fbidx = iminor(inode);
struct fb_info *info = registered_fb[fbidx];
struct fb_ops *fb = info->fbops;
long ret = -ENOIOCTLCMD;

mutex_lock(&info->lock);
switch(cmd) {
case FBIOGET_VSCREENINFO:
case FBIOPUT_VSCREENINFO:
Expand All @@ -1292,7 +1296,6 @@ __releases(&info->lock)
ret = fb->fb_compat_ioctl(info, cmd, arg);
break;
}
mutex_unlock(&info->lock);
return ret;
}
#endif
Expand Down
15 changes: 15 additions & 0 deletions include/linux/fb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -960,6 +960,21 @@ extern struct fb_info *registered_fb[FB_MAX];
extern int num_registered_fb;
extern struct class *fb_class;

static inline int lock_fb_info(struct fb_info *info)
{
mutex_lock(&info->lock);
if (!info->fbops) {
mutex_unlock(&info->lock);
return 0;
}
return 1;
}

static inline void unlock_fb_info(struct fb_info *info)
{
mutex_unlock(&info->lock);
}

static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
u8 *src, u32 s_pitch, u32 height)
{
Expand Down

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