From 4ab59c3c638c6c8952bf07739805d20eb6358a4d Mon Sep 17 00:00:00 2001 From: Sumit Semwal Date: Thu, 11 Jun 2020 17:14:18 +0530 Subject: [PATCH 1/2] dma-buf: Move dma_buf_release() from fops to dentry_ops Charan Teja reported a 'use-after-free' in dmabuffs_dname [1], which happens if the dma_buf_release() is called while the userspace is accessing the dma_buf pseudo fs's dmabuffs_dname() in another process, and dma_buf_release() releases the dmabuf object when the last reference to the struct file goes away. I discussed with Arnd Bergmann, and he suggested that rather than tying the dma_buf_release() to the file_operations' release(), we can tie it to the dentry_operations' d_release(), which will be called when the last ref to the dentry is removed. The path exercised by __fput() calls f_op->release() first, and then calls dput, which eventually calls d_op->d_release(). In the 'normal' case, when no userspace access is happening via dma_buf pseudo fs, there should be exactly one fd, file, dentry and inode, so closing the fd will kill of everything right away. In the presented case, the dentry's d_release() will be called only when the dentry's last ref is released. Therefore, lets move dma_buf_release() from fops->release() to d_ops->d_release() Many thanks to Arnd for his FS insights :) [1]: https://lore.kernel.org/patchwork/patch/1238278/ Fixes: bb2bb9030425 ("dma-buf: add DMA_BUF_SET_NAME ioctls") Reported-by: syzbot+3643a18836bce555bff6@syzkaller.appspotmail.com Cc: [5.3+] Cc: Arnd Bergmann Reported-by: Charan Teja Reddy Reviewed-by: Arnd Bergmann Signed-off-by: Sumit Semwal Tested-by: Charan Teja Reddy Link: https://patchwork.freedesktop.org/patch/msgid/20200611114418.19852-1-sumit.semwal@linaro.org --- drivers/dma-buf/dma-buf.c | 54 ++++++++++++++++++--------------------- 1 file changed, 25 insertions(+), 29 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 01ce125f8e8d..412629601ad3 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -54,37 +54,11 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) dentry->d_name.name, ret > 0 ? name : ""); } -static const struct dentry_operations dma_buf_dentry_ops = { - .d_dname = dmabuffs_dname, -}; - -static struct vfsmount *dma_buf_mnt; - -static int dma_buf_fs_init_context(struct fs_context *fc) -{ - struct pseudo_fs_context *ctx; - - ctx = init_pseudo(fc, DMA_BUF_MAGIC); - if (!ctx) - return -ENOMEM; - ctx->dops = &dma_buf_dentry_ops; - return 0; -} - -static struct file_system_type dma_buf_fs_type = { - .name = "dmabuf", - .init_fs_context = dma_buf_fs_init_context, - .kill_sb = kill_anon_super, -}; - -static int dma_buf_release(struct inode *inode, struct file *file) +static void dma_buf_release(struct dentry *dentry) { struct dma_buf *dmabuf; - if (!is_dma_buf_file(file)) - return -EINVAL; - - dmabuf = file->private_data; + dmabuf = dentry->d_fsdata; BUG_ON(dmabuf->vmapping_counter); @@ -110,9 +84,32 @@ static int dma_buf_release(struct inode *inode, struct file *file) module_put(dmabuf->owner); kfree(dmabuf->name); kfree(dmabuf); +} + +static const struct dentry_operations dma_buf_dentry_ops = { + .d_dname = dmabuffs_dname, + .d_release = dma_buf_release, +}; + +static struct vfsmount *dma_buf_mnt; + +static int dma_buf_fs_init_context(struct fs_context *fc) +{ + struct pseudo_fs_context *ctx; + + ctx = init_pseudo(fc, DMA_BUF_MAGIC); + if (!ctx) + return -ENOMEM; + ctx->dops = &dma_buf_dentry_ops; return 0; } +static struct file_system_type dma_buf_fs_type = { + .name = "dmabuf", + .init_fs_context = dma_buf_fs_init_context, + .kill_sb = kill_anon_super, +}; + static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) { struct dma_buf *dmabuf; @@ -412,7 +409,6 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) } static const struct file_operations dma_buf_fops = { - .release = dma_buf_release, .mmap = dma_buf_mmap_internal, .llseek = dma_buf_llseek, .poll = dma_buf_poll, From bda8eaa6dee7525f4dac950810a85a88bf6c2ba0 Mon Sep 17 00:00:00 2001 From: Chen-Yu Tsai Date: Mon, 29 Jun 2020 14:00:32 +0800 Subject: [PATCH 2/2] drm: sun4i: hdmi: Remove extra HPD polling The HPD sense mechanism in Allwinner's old HDMI encoder hardware is more or less an input-only GPIO. Other GPIO-based HPD implementations directly return the current state, instead of polling for a specific state and returning the other if that times out. Remove the I/O polling from sun4i_hdmi_connector_detect() and directly return a known state based on the current reading. This also gets rid of excessive CPU usage by kworker as reported on Stack Exchange [1] and Armbian forums [2]. [1] https://superuser.com/questions/1515001/debian-10-buster-on-cubietruck-with-bug-in-sun4i-drm-hdmi [2] https://forum.armbian.com/topic/14282-headless-systems-and-sun4i_drm_hdmi-a10a20/ Fixes: 9c5681011a0c ("drm/sun4i: Add HDMI support") Signed-off-by: Chen-Yu Tsai Signed-off-by: Maxime Ripard Link: https://patchwork.freedesktop.org/patch/msgid/20200629060032.24134-1-wens@kernel.org --- drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c index ce07ddc3e058..557cbe5ab35f 100644 --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c @@ -259,9 +259,8 @@ sun4i_hdmi_connector_detect(struct drm_connector *connector, bool force) struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector); unsigned long reg; - if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_HPD_REG, reg, - reg & SUN4I_HDMI_HPD_HIGH, - 0, 500000)) { + reg = readl(hdmi->base + SUN4I_HDMI_HPD_REG); + if (reg & SUN4I_HDMI_HPD_HIGH) { cec_phys_addr_invalidate(hdmi->cec_adap); return connector_status_disconnected; }