FAILED: patch "[PATCH] ALSA: usx2y: bound the hwdep mmap fault offset" failed to apply to 5.10-stable tree

PATCH New [email protected] 2 participants 3 messages Aug 17 – Aug 18

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[email protected]

author maintainer

2026-08-17 13:11 UTC #0 lore raw

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 2ca1eea3cd17930daffe9e429a7c89232036ec24
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026081720-deviant-snipping-e432@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2ca1eea3cd17930daffe9e429a7c89232036ec24 Mon Sep 17 00:00:00 2001
From: Baul Lee <[email protected]>
Date: Wed, 5 Aug 2026 10:34:45 +0900
Subject: [PATCH] ALSA: usx2y: bound the hwdep mmap fault offset

snd_us428ctls_vm_fault() turns the faulting page offset into a kernel address with no bound of any kind:

	offset = vmf->pgoff << PAGE_SHIFT;
	vaddr = (char *)(...)->us428ctls_sharedmem + offset;
	page = virt_to_page(vaddr);
	get_page(page);
	vmf->page = page;

	return 0;

snd_us428ctls_mmap() checks only the length of the mapping, never the offset, and us428ctls_sharedmem is a single page from alloc_pages_exact(). For a character device file_mmap_size_max() returns ULONG_MAX, so the mm layer imposes no ceiling either. Every page offset above zero resolves to a struct page outside the object, and the handler installs it into the caller's address space read-write; the vma is not marked read-only.

The caller picks the page frame with a single mmap() argument and gets read-write access to a page of kernel memory it does not own; an offset that lands in an unpopulated vmemmap region oopses instead.

A process that can open the hwdep node of an attached US-X2Y reaches this after loading the FPGA image through the same node; no capability check is involved.

On 7.2.0-rc5 (arm64), mmap() with a large offset:

  Unable to handle kernel paging request at virtual address fffffdffc45d5ac8
  pc : snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y]
  Call trace:
   snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y]
   __do_fault
   __handle_mm_fault
   handle_mm_fault
   el0_da

Reject any offset outside the shared region. The pcm hwdep handler in usx2yhwdeppcm.c computes its address the same way and needs the same bound.

Discovered by XBOW, triaged by Baul Lee <[email protected]>

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Reported-by Federico Kirschbaum <[email protected]>

Reported-by Baul Lee <[email protected]>

Cc [email protected]

Signed-off-by Baul Lee <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Takashi Iwai <[email protected]>

sound/usb/usx2y/usX2Yhwdep.c +2 -0

index 4d7925184826..7f153a2fcdd8 100644
@@ -25,6 +25,8 @@ static vm_fault_t snd_us428ctls_vm_fault(struct vm_fault *vmf)
 	void *vaddr;
 
 	offset = vmf->pgoff << PAGE_SHIFT;
+	if (offset >= US428_SHAREDMEM_PAGES)
+		return VM_FAULT_SIGBUS;
 	vaddr = (char *)((struct usx2ydev *)vmf->vma->vm_private_data)->us428ctls_sharedmem + offset;
 	page = virt_to_page(vaddr);
 	get_page(page);

sound/usb/usx2y/usx2yhwdeppcm.c +2 -0

index 7c90214485d9..f1d5b4b797ad 100644
@@ -672,6 +672,8 @@ static vm_fault_t snd_usx2y_hwdep_pcm_vm_fault(struct vm_fault *vmf)
 	void *vaddr;
 
 	offset = vmf->pgoff << PAGE_SHIFT;
+	if (offset >= USX2Y_HWDEP_PCM_PAGES)
+		return VM_FAULT_SIGBUS;
 	vaddr = (char *)((struct usx2ydev *)vmf->vma->vm_private_data)->hwdep_pcm_shm + offset;
 	vmf->page = virt_to_page(vaddr);
 	get_page(vmf->page);

Sasha Levin

maintainer

2026-08-18 17:57 UTC #1 lore raw

PATCH 1/2 ALSA: usx2y: Fix potential leaks of uninitialized memory

From: Takashi Iwai <[email protected]>

[ Upstream commit 4e268db74770b454b877ab5260f1868a457d212c ]

usx2y drivers may expose the allocated pages via mmap, but it performs zero-clear only for the struct size, not aligned with the page size. This leaves out some uninitialized trailing bytes.

This patch fixes the clearance to cover all memory that are exposed to user-space.

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Takashi Iwai <[email protected]>

Stable-dep-of: 2ca1eea3cd17 ("ALSA: usx2y: bound the hwdep mmap fault offset")

Signed-off-by Sasha Levin <[email protected]>

---
 sound/usb/usx2y/usX2Yhwdep.c      |  8 ++++----
 sound/usb/usx2y/usbus428ctldefs.h |  2 ++
 sound/usb/usx2y/usbusx2y.c        |  2 +-
 sound/usb/usx2y/usx2yhwdeppcm.c   | 13 ++++++++-----
 4 files changed, 15 insertions(+), 10 deletions(-)

sound/usb/usx2y/usX2Yhwdep.c +4 -4

index 2d4e943be2da..0ed50be89271 100644
@@ -55,17 +55,17 @@ static int snd_us428ctls_mmap(struct snd_hwdep *hw, struct file *filp, struct vm
 		return -EBUSY;
 
 	/* if userspace tries to mmap beyond end of our buffer, fail */
-	if (size > PAGE_ALIGN(sizeof(struct us428ctls_sharedmem))) {
-		snd_printd("%lu > %lu\n", size, (unsigned long)sizeof(struct us428ctls_sharedmem));
+	if (size > US428_SHAREDMEM_PAGES) {
+		snd_printd("%lu > %lu\n", size, (unsigned long)US428_SHAREDMEM_PAGES);
 		return -EINVAL;
 	}
 
 	if (!us428->us428ctls_sharedmem) {
 		init_waitqueue_head(&us428->us428ctls_wait_queue_head);
-		us428->us428ctls_sharedmem = alloc_pages_exact(sizeof(struct us428ctls_sharedmem), GFP_KERNEL);
+		us428->us428ctls_sharedmem = alloc_pages_exact(US428_SHAREDMEM_PAGES, GFP_KERNEL);
 		if (!us428->us428ctls_sharedmem)
 			return -ENOMEM;
-		memset(us428->us428ctls_sharedmem, -1, sizeof(struct us428ctls_sharedmem));
+		memset(us428->us428ctls_sharedmem, -1, US428_SHAREDMEM_PAGES);
 		us428->us428ctls_sharedmem->ctl_snapshot_last = -2;
 	}
 	area->vm_ops = &us428ctls_vm_ops;

sound/usb/usx2y/usbus428ctldefs.h +2 -0

index 06b27d23d3c2..9ba15d974e63 100644
@@ -89,3 +89,5 @@ struct us428ctls_sharedmem {
 	struct us428_p4out	p4out[N_US428_P4OUT_BUFS];
 	int			p4out_last, p4out_sent;
 };
+
+#define US428_SHAREDMEM_PAGES	PAGE_ALIGN(sizeof(struct us428ctls_sharedmem))

sound/usb/usx2y/usbusx2y.c +1 -1

index 34d5f5379632..ac584795606c 100644
@@ -376,7 +376,7 @@ static void snd_usx2y_card_private_free(struct snd_card *card)
 	usb_free_urb(usx2y->in04_urb);
 	if (usx2y->us428ctls_sharedmem)
 		free_pages_exact(usx2y->us428ctls_sharedmem,
-				 sizeof(*usx2y->us428ctls_sharedmem));
+				 US428_SHAREDMEM_PAGES);
 	if (usx2y->card_index >= 0 && usx2y->card_index < SNDRV_CARDS)
 		snd_usx2y_card_used[usx2y->card_index] = 0;
 }

sound/usb/usx2y/usx2yhwdeppcm.c +8 -5

index 9219341d71c7..b988a4870de4 100644
@@ -485,6 +485,9 @@ static int usx2y_usbpcm_urbs_start(struct snd_usx2y_substream *subs)
 	return err;
 }
 
+#define USX2Y_HWDEP_PCM_PAGES	\
+	PAGE_ALIGN(sizeof(struct snd_usx2y_hwdep_pcm_shm))
+
 /*
  * prepare callback
  *

@@ -501,11 +504,11 @@ static int snd_usx2y_usbpcm_prepare(struct snd_pcm_substream *substream)
 	snd_printdd("snd_usx2y_pcm_prepare(%p)\n", substream);
 
 	if (!usx2y->hwdep_pcm_shm) {
-		usx2y->hwdep_pcm_shm = alloc_pages_exact(sizeof(struct snd_usx2y_hwdep_pcm_shm),
+		usx2y->hwdep_pcm_shm = alloc_pages_exact(USX2Y_HWDEP_PCM_PAGES,
 							 GFP_KERNEL);
 		if (!usx2y->hwdep_pcm_shm)
 			return -ENOMEM;
-		memset(usx2y->hwdep_pcm_shm, 0, sizeof(struct snd_usx2y_hwdep_pcm_shm));
+		memset(usx2y->hwdep_pcm_shm, 0, USX2Y_HWDEP_PCM_PAGES);
 	}
 
 	mutex_lock(&usx2y->pcm_mutex);

@@ -692,8 +695,8 @@ static int snd_usx2y_hwdep_pcm_mmap(struct snd_hwdep *hw, struct file *filp, str
 		return -EBUSY;
 
 	/* if userspace tries to mmap beyond end of our buffer, fail */
-	if (size > PAGE_ALIGN(sizeof(struct snd_usx2y_hwdep_pcm_shm))) {
-		snd_printd("%lu > %lu\n", size, (unsigned long)sizeof(struct snd_usx2y_hwdep_pcm_shm));
+	if (size > USX2Y_HWDEP_PCM_PAGES) {
+		snd_printd("%lu > %lu\n", size, (unsigned long)USX2Y_HWDEP_PCM_PAGES);
 		return -EINVAL;
 	}

@@ -711,7 +714,7 @@ static void snd_usx2y_hwdep_pcm_private_free(struct snd_hwdep *hwdep)
 	struct usx2ydev *usx2y = hwdep->private_data;
 
 	if (usx2y->hwdep_pcm_shm)
-		free_pages_exact(usx2y->hwdep_pcm_shm, sizeof(struct snd_usx2y_hwdep_pcm_shm));
+		free_pages_exact(usx2y->hwdep_pcm_shm, USX2Y_HWDEP_PCM_PAGES);
 }
 
 int usx2y_hwdep_pcm_new(struct snd_card *card)

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-08-18 17:57 UTC #2 lore raw

PATCH 2/2 ALSA: usx2y: bound the hwdep mmap fault offset

From: Baul Lee <[email protected]>

[ Upstream commit 2ca1eea3cd17930daffe9e429a7c89232036ec24 ]

snd_us428ctls_vm_fault() turns the faulting page offset into a kernel address with no bound of any kind:

	offset = vmf->pgoff << PAGE_SHIFT;
	vaddr = (char *)(...)->us428ctls_sharedmem + offset;
	page = virt_to_page(vaddr);
	get_page(page);
	vmf->page = page;

	return 0;

A process that can open the hwdep node of an attached US-X2Y reaches this after loading the FPGA image through the same node; no capability check is involved.

On 7.2.0-rc5 (arm64), mmap() with a large offset:

  Unable to handle kernel paging request at virtual address fffffdffc45d5ac8
  pc : snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y]
  Call trace:
   snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y]
   __do_fault
   __handle_mm_fault
   handle_mm_fault
   el0_da

Reject any offset outside the shared region. The pcm hwdep handler in usx2yhwdeppcm.c computes its address the same way and needs the same bound.

Discovered by XBOW, triaged by Baul Lee <[email protected]>

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Reported-by Federico Kirschbaum <[email protected]>

Reported-by Baul Lee <[email protected]>

Cc [email protected]

Signed-off-by Baul Lee <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Takashi Iwai <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 sound/usb/usx2y/usX2Yhwdep.c    | 2 ++
 sound/usb/usx2y/usx2yhwdeppcm.c | 2 ++
 2 files changed, 4 insertions(+)

sound/usb/usx2y/usX2Yhwdep.c +2 -0

index 0ed50be89271..eeafe580d038 100644
@@ -29,6 +29,8 @@ static vm_fault_t snd_us428ctls_vm_fault(struct vm_fault *vmf)
 		   vmf->pgoff);
 
 	offset = vmf->pgoff << PAGE_SHIFT;
+	if (offset >= US428_SHAREDMEM_PAGES)
+		return VM_FAULT_SIGBUS;
 	vaddr = (char *)((struct usx2ydev *)vmf->vma->vm_private_data)->us428ctls_sharedmem + offset;
 	page = virt_to_page(vaddr);
 	get_page(page);

sound/usb/usx2y/usx2yhwdeppcm.c +2 -0

index b988a4870de4..3f6e87f30f7e 100644
@@ -674,6 +674,8 @@ static vm_fault_t snd_usx2y_hwdep_pcm_vm_fault(struct vm_fault *vmf)
 	void *vaddr;
 
 	offset = vmf->pgoff << PAGE_SHIFT;
+	if (offset >= USX2Y_HWDEP_PCM_PAGES)
+		return VM_FAULT_SIGBUS;
 	vaddr = (char *)((struct usx2ydev *)vmf->vma->vm_private_data)->hwdep_pcm_shm + offset;
 	vmf->page = virt_to_page(vaddr);
 	get_page(vmf->page);

Signature · 1 line

2.53.0