From cb57469c9573f6018cd1302953dd45d6e05aba7b Mon Sep 17 00:00:00 2001 From: Joel Fernandes Date: Fri, 16 Feb 2018 11:02:01 -0800 Subject: [PATCH 1/3] staging: android: ashmem: Fix lockdep issue during llseek ashmem_mutex create a chain of dependencies like so: (1) mmap syscall -> mmap_sem -> (acquired) ashmem_mmap ashmem_mutex (try to acquire) (block) (2) llseek syscall -> ashmem_llseek -> ashmem_mutex -> (acquired) inode_lock -> inode->i_rwsem (try to acquire) (block) (3) getdents -> iterate_dir -> inode_lock -> inode->i_rwsem (acquired) copy_to_user -> mmap_sem (try to acquire) There is a lock ordering created between mmap_sem and inode->i_rwsem causing a lockdep splat [2] during a syzcaller test, this patch fixes the issue by unlocking the mutex earlier. Functionally that's Ok since we don't need to protect vfs_llseek. [1] https://patchwork.kernel.org/patch/10185031/ [2] https://lkml.org/lkml/2018/1/10/48 Acked-by: Todd Kjos Cc: Arve Hjonnevag Cc: stable@vger.kernel.org Reported-by: syzbot+8ec30bb7bf1a981a2012@syzkaller.appspotmail.com Signed-off-by: Joel Fernandes Acked-by: Greg Hackmann Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ashmem.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 6dbba5aff191..d5450365769c 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -326,24 +326,23 @@ static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin) mutex_lock(&ashmem_mutex); if (asma->size == 0) { - ret = -EINVAL; - goto out; + mutex_unlock(&ashmem_mutex); + return -EINVAL; } if (!asma->file) { - ret = -EBADF; - goto out; + mutex_unlock(&ashmem_mutex); + return -EBADF; } + mutex_unlock(&ashmem_mutex); + ret = vfs_llseek(asma->file, offset, origin); if (ret < 0) - goto out; + return ret; /** Copy f_pos from backing file, since f_ops->llseek() sets it */ file->f_pos = asma->file->f_pos; - -out: - mutex_unlock(&ashmem_mutex); return ret; } From a42ae5905140c324362fe5036ae1dbb16e4d359c Mon Sep 17 00:00:00 2001 From: Frank Mori Hess Date: Thu, 15 Feb 2018 15:13:42 -0500 Subject: [PATCH 2/3] staging: comedi: fix comedi_nsamples_left. A rounding error was causing comedi_nsamples_left to return the wrong value when nsamples was not a multiple of the scan length. Cc: # v4.4+ Signed-off-by: Frank Mori Hess Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c index e618a87521a3..9d733471ca2e 100644 --- a/drivers/staging/comedi/drivers.c +++ b/drivers/staging/comedi/drivers.c @@ -475,8 +475,7 @@ unsigned int comedi_nsamples_left(struct comedi_subdevice *s, struct comedi_cmd *cmd = &async->cmd; if (cmd->stop_src == TRIG_COUNT) { - unsigned int nscans = nsamples / cmd->scan_end_arg; - unsigned int scans_left = __comedi_nscans_left(s, nscans); + unsigned int scans_left = __comedi_nscans_left(s, cmd->stop_arg); unsigned int scan_pos = comedi_bytes_to_samples(s, async->scan_progress); unsigned long long samples_left = 0; From 740a5759bf222332fbb5eda42f89aa25ba38f9b2 Mon Sep 17 00:00:00 2001 From: Yisheng Xie Date: Wed, 28 Feb 2018 14:59:22 +0800 Subject: [PATCH 3/3] staging: android: ashmem: Fix possible deadlock in ashmem_ioctl ashmem_mutex may create a chain of dependencies like: CPU0 CPU1 mmap syscall ioctl syscall -> mmap_sem (acquired) -> ashmem_ioctl -> ashmem_mmap -> ashmem_mutex (acquired) -> ashmem_mutex (try to acquire) -> copy_from_user -> mmap_sem (try to acquire) There is a lock odering problem between mmap_sem and ashmem_mutex causing a lockdep splat[1] during a syzcaller test. This patch fixes the problem by move copy_from_user out of ashmem_mutex. [1] https://www.spinics.net/lists/kernel/msg2733200.html Fixes: ce8a3a9e76d0 (staging: android: ashmem: Fix a race condition in pin ioctls) Reported-by: syzbot+d7a918a7a8e1c952bc36@syzkaller.appspotmail.com Signed-off-by: Yisheng Xie Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ashmem.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index d5450365769c..86580b6df33d 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -701,16 +701,14 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, size_t pgstart, pgend; int ret = -EINVAL; + if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) + return -EFAULT; + mutex_lock(&ashmem_mutex); if (unlikely(!asma->file)) goto out_unlock; - if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) { - ret = -EFAULT; - goto out_unlock; - } - /* per custom, you can pass zero for len to mean "everything onward" */ if (!pin.len) pin.len = PAGE_ALIGN(asma->size) - pin.offset;