From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Righi Date: Sun, 06 Feb 2011 15:50:24 +0000 Subject: [PATCH] fb: fix potential deadlock between lock_fb_info and console_lock Message-Id: <1297007424-14656-1-git-send-email-arighi@develer.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Andrew Morton Cc: Greg KH , =?UTF-8?q?Peter=20Nordstr=C3=B6m=20=28Palm=20GBU=29?= , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org The function fb_set_suspend() must be called with the console semaphore held, which means the code path coming in here will first take the console_lock() and then call lock_fb_info(). However several framebuffer ioctl commands acquire these locks in reverse order (lock_fb_info() and then console_lock()). This gives rise to potential AB-BA deadlock. Fix this by changing the order of acquisition in the ioctl commands that make use of console_lock(). Reported-by: Peter Nordstr=C3=B6m (Palm GBU) Signed-off-by: Andrea Righi --- drivers/video/fbmem.c | 24 +++++++++++++++--------- 1 files changed, 15 insertions(+), 9 deletions(-) diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c index e2bf953..def59f0 100644 --- a/drivers/video/fbmem.c +++ b/drivers/video/fbmem.c @@ -1034,14 +1034,16 @@ static long do_fb_ioctl(struct fb_info *info, unsig= ned int cmd, case FBIOPUT_VSCREENINFO: if (copy_from_user(&var, argp, sizeof(var))) return -EFAULT; - if (!lock_fb_info(info)) - return -ENODEV; console_lock(); + if (!lock_fb_info(info)) { + console_unlock(); + return -ENODEV; + } info->flags |=3D FBINFO_MISC_USEREVENT; ret =3D fb_set_var(info, &var); info->flags &=3D ~FBINFO_MISC_USEREVENT; - console_unlock(); unlock_fb_info(info); + console_unlock(); if (!ret && copy_to_user(argp, &var, sizeof(var))) ret =3D -EFAULT; break; @@ -1070,12 +1072,14 @@ static long do_fb_ioctl(struct fb_info *info, unsig= ned int cmd, case FBIOPAN_DISPLAY: if (copy_from_user(&var, argp, sizeof(var))) return -EFAULT; - if (!lock_fb_info(info)) - return -ENODEV; console_lock(); + if (!lock_fb_info(info)) { + console_unlock(); + return -ENODEV; + } ret =3D fb_pan_display(info, &var); - console_unlock(); unlock_fb_info(info); + console_unlock(); if (ret =3D 0 && copy_to_user(argp, &var, sizeof(var))) return -EFAULT; break; @@ -1117,14 +1121,16 @@ static long do_fb_ioctl(struct fb_info *info, unsig= ned int cmd, unlock_fb_info(info); break; case FBIOBLANK: - if (!lock_fb_info(info)) - return -ENODEV; console_lock(); + if (!lock_fb_info(info)) { + console_unlock(); + return -ENODEV; + } info->flags |=3D FBINFO_MISC_USEREVENT; ret =3D fb_blank(info, arg); info->flags &=3D ~FBINFO_MISC_USEREVENT; - console_unlock(); unlock_fb_info(info); + console_unlock(); break; default: if (!lock_fb_info(info)) --=20 1.7.1