From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 051D73E4C97; Tue, 5 May 2026 07:31:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777966296; cv=none; b=UKHVPijC3pkAcWMhQBxx25+a5Wx/6AHPipjXKHC3hgZPGexmh4/kvoNLwktapKOoaTjtBe8zYlzpllIM2MORNFEiYutUASnl2akPvcbdKosHyYBUBFPDqNs90a0F22OE1BEWJ0Rl480JOdi4693Jpd645F7Vo7un+gXKmYym+SM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777966296; c=relaxed/simple; bh=9gOsdwvhHrbZhGP74GCYkzafcjxSWWQ4PZ9lonxqf2o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YIole1Sfb+P00e/PYcrQuIh9Ec+B3zptg2NuMavd4UW26wASvGLpYjRwXMfIqsQTVaxiW5lJAX3PKD8MbAhmwi4eHAwg2hfyw7Arld1HO4gUauTN4rhO8cAS1gezoQjbX1X7i50Tl6Rluc48dTnvOwH9k7n4jBEEQw18Y0y/Tfk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ex/bm3ug; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ex/bm3ug" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51CDAC2BCB4; Tue, 5 May 2026 07:31:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777966295; bh=9gOsdwvhHrbZhGP74GCYkzafcjxSWWQ4PZ9lonxqf2o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ex/bm3ugvPQf79namjCWn+vHMhYTjzvjRmx+9G/z0hxDQpNppeV4dkpGrx4/uK9fI qOyH1zF1IAnb8IOMPymAg0PC96X5f2dfCzPFJ7scxprQEcagPfzVwfhMG2TfQCfYyl EkKshwxzlrjniN7KRVrdCQh6n6x/GrEk6RhAf7KpMSSvZAR6GN416d35P38iX3Zg7/ gPZpgS0qyr2ndWaMf8qtlir0zdQn9aVROX0vdeyg66sOmIkZrGkjWYKHq2pPfDqu3m tVUc1zdCMS7ZKss4ojcEMM+6q4pEB5jYO9K5WavtYcGvbQgxJVgasGUGkNDHc+fKX3 C0xYKnAj27q1A== From: Sasha Levin To: stable@vger.kernel.org Cc: Thomas Zimmermann , Helge Deller , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Sasha Levin Subject: [PATCH 6.1.y] fbdev: defio: Disconnect deferred I/O from the lifetime of struct fb_info Date: Tue, 5 May 2026 03:31:29 -0400 Message-ID: <20260505073129.414475-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026050117-caravan-atrocious-ee79@gregkh> References: <2026050117-caravan-atrocious-ee79@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Thomas Zimmermann [ Upstream commit 9ded47ad003f09a94b6a710b5c47f4aa5ceb7429 ] Hold state of deferred I/O in struct fb_deferred_io_state. Allocate an instance as part of initializing deferred I/O and remove it only after the final mapping has been closed. If the fb_info and the contained deferred I/O meanwhile goes away, clear struct fb_deferred_io_state.info to invalidate the mapping. Any access will then result in a SIGBUS signal. Fixes a long-standing problem, where a device hot-unplug happens while user space still has an active mapping of the graphics memory. The hot- unplug frees the instance of struct fb_info. Accessing the memory will operate on undefined state. Signed-off-by: Thomas Zimmermann Fixes: 60b59beafba8 ("fbdev: mm: Deferred IO support") Cc: Helge Deller Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: stable@vger.kernel.org # v2.6.22+ Signed-off-by: Helge Deller [ context + _obj() conversion ] Signed-off-by: Sasha Levin --- drivers/video/fbdev/core/fb_defio.c | 164 ++++++++++++++++++++++++---- include/linux/fb.h | 4 +- 2 files changed, 145 insertions(+), 23 deletions(-) diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index 3b376345d4d47..7ac0bf4766b34 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -23,6 +23,75 @@ #include #include +/* + * struct fb_deferred_io_state + */ + +struct fb_deferred_io_state { + struct kref ref; + + struct mutex lock; /* mutex that protects the pageref list */ + /* fields protected by lock */ + struct fb_info *info; +}; + +static struct fb_deferred_io_state *fb_deferred_io_state_alloc(void) +{ + struct fb_deferred_io_state *fbdefio_state; + + fbdefio_state = kzalloc(sizeof(*fbdefio_state), GFP_KERNEL); + if (!fbdefio_state) + return NULL; + + kref_init(&fbdefio_state->ref); + mutex_init(&fbdefio_state->lock); + + return fbdefio_state; +} + +static void fb_deferred_io_state_release(struct fb_deferred_io_state *fbdefio_state) +{ + mutex_destroy(&fbdefio_state->lock); + + kfree(fbdefio_state); +} + +static void fb_deferred_io_state_get(struct fb_deferred_io_state *fbdefio_state) +{ + kref_get(&fbdefio_state->ref); +} + +static void __fb_deferred_io_state_release(struct kref *ref) +{ + struct fb_deferred_io_state *fbdefio_state = + container_of(ref, struct fb_deferred_io_state, ref); + + fb_deferred_io_state_release(fbdefio_state); +} + +static void fb_deferred_io_state_put(struct fb_deferred_io_state *fbdefio_state) +{ + kref_put(&fbdefio_state->ref, __fb_deferred_io_state_release); +} + +/* + * struct vm_operations_struct + */ + +static void fb_deferred_io_vm_open(struct vm_area_struct *vma) +{ + struct fb_deferred_io_state *fbdefio_state = vma->vm_private_data; + + fb_deferred_io_state_get(fbdefio_state); +} + +static void fb_deferred_io_vm_close(struct vm_area_struct *vma) +{ + struct fb_deferred_io_state *fbdefio_state = vma->vm_private_data; + + fb_deferred_io_state_put(fbdefio_state); +} + static struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs) { void *screen_base = (void __force *) info->screen_base; @@ -93,17 +162,31 @@ static void fb_deferred_io_pageref_put(struct fb_deferred_io_pageref *pageref, /* this is to find and return the vmalloc-ed fb pages */ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf) { + struct fb_info *info; unsigned long offset; struct page *page; - struct fb_info *info = vmf->vma->vm_private_data; + vm_fault_t ret; + struct fb_deferred_io_state *fbdefio_state = vmf->vma->vm_private_data; + + mutex_lock(&fbdefio_state->lock); + + info = fbdefio_state->info; + if (!info) { + ret = VM_FAULT_SIGBUS; /* our device is gone */ + goto err_mutex_unlock; + } offset = vmf->pgoff << PAGE_SHIFT; - if (offset >= info->fix.smem_len) - return VM_FAULT_SIGBUS; + if (offset >= info->fix.smem_len) { + ret = VM_FAULT_SIGBUS; + goto err_mutex_unlock; + } page = fb_deferred_io_page(info, offset); - if (!page) - return VM_FAULT_SIGBUS; + if (!page) { + ret = VM_FAULT_SIGBUS; + goto err_mutex_unlock; + } get_page(page); @@ -115,8 +198,15 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf) BUG_ON(!page->mapping); page->index = vmf->pgoff; /* for page_mkclean() */ + mutex_unlock(&fbdefio_state->lock); + vmf->page = page; + return 0; + +err_mutex_unlock: + mutex_unlock(&fbdefio_state->lock); + return ret; } int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasync) @@ -143,15 +233,24 @@ EXPORT_SYMBOL_GPL(fb_deferred_io_fsync); * Adds a page to the dirty list. Call this from struct * vm_operations_struct.page_mkwrite. */ -static vm_fault_t fb_deferred_io_track_page(struct fb_info *info, unsigned long offset, - struct page *page) +static vm_fault_t fb_deferred_io_track_page(struct fb_deferred_io_state *fbdefio_state, + unsigned long offset, struct page *page) { - struct fb_deferred_io *fbdefio = info->fbdefio; + struct fb_info *info; + struct fb_deferred_io *fbdefio; struct fb_deferred_io_pageref *pageref; vm_fault_t ret; /* protect against the workqueue changing the page list */ - mutex_lock(&fbdefio->lock); + mutex_lock(&fbdefio_state->lock); + + info = fbdefio_state->info; + if (!info) { + ret = VM_FAULT_SIGBUS; /* our device is gone */ + goto err_mutex_unlock; + } + + fbdefio = info->fbdefio; /* first write in this cycle, notify the driver */ if (fbdefio->first_io && list_empty(&fbdefio->pagereflist)) @@ -173,14 +272,14 @@ static vm_fault_t fb_deferred_io_track_page(struct fb_info *info, unsigned long */ lock_page(pageref->page); - mutex_unlock(&fbdefio->lock); + mutex_unlock(&fbdefio_state->lock); /* come back after delay to process the deferred IO */ schedule_delayed_work(&info->deferred_work, fbdefio->delay); return VM_FAULT_LOCKED; err_mutex_unlock: - mutex_unlock(&fbdefio->lock); + mutex_unlock(&fbdefio_state->lock); return ret; } @@ -198,25 +297,28 @@ static vm_fault_t fb_deferred_io_track_page(struct fb_info *info, unsigned long * Returns: * VM_FAULT_LOCKED on success, or a VM_FAULT error otherwise. */ -static vm_fault_t fb_deferred_io_page_mkwrite(struct fb_info *info, struct vm_fault *vmf) +static vm_fault_t fb_deferred_io_page_mkwrite(struct fb_deferred_io_state *fbdefio_state, + struct vm_fault *vmf) { unsigned long offset = vmf->pgoff << PAGE_SHIFT; struct page *page = vmf->page; file_update_time(vmf->vma->vm_file); - return fb_deferred_io_track_page(info, offset, page); + return fb_deferred_io_track_page(fbdefio_state, offset, page); } /* vm_ops->page_mkwrite handler */ static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf) { - struct fb_info *info = vmf->vma->vm_private_data; + struct fb_deferred_io_state *fbdefio_state = vmf->vma->vm_private_data; - return fb_deferred_io_page_mkwrite(info, vmf); + return fb_deferred_io_page_mkwrite(fbdefio_state, vmf); } static const struct vm_operations_struct fb_deferred_io_vm_ops = { + .open = fb_deferred_io_vm_open, + .close = fb_deferred_io_vm_close, .fault = fb_deferred_io_fault, .page_mkwrite = fb_deferred_io_mkwrite, }; @@ -231,7 +333,10 @@ int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma) vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; if (!(info->flags & FBINFO_VIRTFB)) vma->vm_flags |= VM_IO; - vma->vm_private_data = info; + vma->vm_private_data = info->fbdefio_state; + + fb_deferred_io_state_get(info->fbdefio_state); /* released in vma->vm_ops->close() */ + return 0; } EXPORT_SYMBOL_GPL(fb_deferred_io_mmap); @@ -242,9 +347,10 @@ static void fb_deferred_io_work(struct work_struct *work) struct fb_info *info = container_of(work, struct fb_info, deferred_work.work); struct fb_deferred_io_pageref *pageref, *next; struct fb_deferred_io *fbdefio = info->fbdefio; + struct fb_deferred_io_state *fbdefio_state = info->fbdefio_state; /* here we mkclean the pages, then do all deferred IO */ - mutex_lock(&fbdefio->lock); + mutex_lock(&fbdefio_state->lock); list_for_each_entry(pageref, &fbdefio->pagereflist, list) { struct page *cur = pageref->page; lock_page(cur); @@ -259,12 +365,13 @@ static void fb_deferred_io_work(struct work_struct *work) list_for_each_entry_safe(pageref, next, &fbdefio->pagereflist, list) fb_deferred_io_pageref_put(pageref, info); - mutex_unlock(&fbdefio->lock); + mutex_unlock(&fbdefio_state->lock); } int fb_deferred_io_init(struct fb_info *info) { struct fb_deferred_io *fbdefio = info->fbdefio; + struct fb_deferred_io_state *fbdefio_state; struct fb_deferred_io_pageref *pagerefs; unsigned long npagerefs, i; int ret; @@ -274,7 +381,11 @@ int fb_deferred_io_init(struct fb_info *info) if (WARN_ON(!info->fix.smem_len)) return -EINVAL; - mutex_init(&fbdefio->lock); + fbdefio_state = fb_deferred_io_state_alloc(); + if (!fbdefio_state) + return -ENOMEM; + fbdefio_state->info = info; + INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work); INIT_LIST_HEAD(&fbdefio->pagereflist); if (fbdefio->delay == 0) /* set a default of 1 s */ @@ -293,10 +404,12 @@ int fb_deferred_io_init(struct fb_info *info) info->npagerefs = npagerefs; info->pagerefs = pagerefs; + info->fbdefio_state = fbdefio_state; + return 0; err: - mutex_destroy(&fbdefio->lock); + fb_deferred_io_state_release(fbdefio_state); return ret; } EXPORT_SYMBOL_GPL(fb_deferred_io_init); @@ -337,11 +450,18 @@ EXPORT_SYMBOL_GPL(fb_deferred_io_release); void fb_deferred_io_cleanup(struct fb_info *info) { - struct fb_deferred_io *fbdefio = info->fbdefio; + struct fb_deferred_io_state *fbdefio_state = info->fbdefio_state; fb_deferred_io_lastclose(info); + info->fbdefio_state = NULL; + + mutex_lock(&fbdefio_state->lock); + fbdefio_state->info = NULL; + mutex_unlock(&fbdefio_state->lock); + + fb_deferred_io_state_put(fbdefio_state); + kvfree(info->pagerefs); - mutex_destroy(&fbdefio->lock); } EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup); diff --git a/include/linux/fb.h b/include/linux/fb.h index c7f0f14e1f74b..5f94c58c4672e 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -213,12 +213,13 @@ struct fb_deferred_io { unsigned long delay; bool sort_pagereflist; /* sort pagelist by offset */ int open_count; /* number of opened files; protected by fb_info lock */ - struct mutex lock; /* mutex that protects the pageref list */ struct list_head pagereflist; /* list of pagerefs for touched pages */ /* callback */ void (*first_io)(struct fb_info *info); void (*deferred_io)(struct fb_info *info, struct list_head *pagelist); }; + +struct fb_deferred_io_state; #endif /* @@ -479,6 +480,7 @@ struct fb_info { unsigned long npagerefs; struct fb_deferred_io_pageref *pagerefs; struct fb_deferred_io *fbdefio; + struct fb_deferred_io_state *fbdefio_state; #endif const struct fb_ops *fbops; -- 2.53.0