FAILED: patch "[PATCH] iommu/amd: Remove latent out-of-bounds access in IOMMU" failed to apply to 7.0-stable tree

FAILED: patch "[PATCH] iommu/amd: Remove latent out-of-bounds access in IOMMU" failed to apply to 7.0-stable tree

[gregkh]

The patch below does not apply to the 7.0-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 <stable@vger.kernel.org>.

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-7.0.y
git checkout FETCH_HEAD
git cherry-pick -x 8dfd3d8d74435344ee8dc9237596959c8b2a6cbe
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026052054-gimmick-getting-5504@gregkh' --subject-prefix 'PATCH 7.0.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 8dfd3d8d74435344ee8dc9237596959c8b2a6cbe Mon Sep 17 00:00:00 2001
From: Eder Zulian <ezulian@redhat.com>
Date: Fri, 10 Apr 2026 14:55:50 +0200
Subject: [PATCH] iommu/amd: Remove latent out-of-bounds access in IOMMU
 debugfs

In iommu_mmio_write() and iommu_capability_write(), the variables
dbg_mmio_offset and dbg_cap_offset are declared as int. However, they
are populated using kstrtou32_from_user(). If a user provides a
sufficiently large value, it can become a negative integer.

Prior to this patch, the AMD IOMMU debugfs implementation was already
protected by different mechanisms.

1. #define OFS_IN_SZ 8 ensures the user string <= 8 bytes, so
   e.g. 0xffffffff isn't a valid input.

  if (cnt > OFS_IN_SZ)
     return -EINVAL;

2. Implicit type promotion in iommu_mmio_write(), dbg_mmio_offset is int
   and iommu->mmio_phys_end is u64

  if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64))
      return -EINVAL;

3. The show handlers would currently catch the negative number and
   refuse to perform the read.

Replace kstrtou32_from_user() with kstrtos32_from_user() to parse the
input, and check for negative values to explicitly prevent out-of-bounds
memory accesses directly in iommu_mmio_write() and
iommu_capability_write().

Signed-off-by: Eder Zulian <ezulian@redhat.com>
Fixes: 7a4ee419e8c1 ("iommu/amd: Add debugfs support to dump IOMMU MMIO registers")
Cc: stable@vger.kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
index 4e66473d7cea..4c53b6361314 100644
--- a/drivers/iommu/amd/debugfs.c
+++ b/drivers/iommu/amd/debugfs.c
@@ -31,11 +31,12 @@ static ssize_t iommu_mmio_write(struct file *filp, const char __user *ubuf,
 	if (cnt > OFS_IN_SZ)
 		return -EINVAL;
 
-	ret = kstrtou32_from_user(ubuf, cnt, 0, &dbg_mmio_offset);
+	ret = kstrtos32_from_user(ubuf, cnt, 0, &dbg_mmio_offset);
 	if (ret)
 		return ret;
 
-	if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64))
+	if (dbg_mmio_offset < 0 || dbg_mmio_offset >
+			iommu->mmio_phys_end - sizeof(u64))
 		return -EINVAL;
 
 	iommu->dbg_mmio_offset = dbg_mmio_offset;
@@ -71,12 +72,12 @@ static ssize_t iommu_capability_write(struct file *filp, const char __user *ubuf
 	if (cnt > OFS_IN_SZ)
 		return -EINVAL;
 
-	ret = kstrtou32_from_user(ubuf, cnt, 0, &dbg_cap_offset);
+	ret = kstrtos32_from_user(ubuf, cnt, 0, &dbg_cap_offset);
 	if (ret)
 		return ret;
 
 	/* Capability register at offset 0x14 is the last IOMMU capability register. */
-	if (dbg_cap_offset > 0x14)
+	if (dbg_cap_offset < 0 || dbg_cap_offset > 0x14)
 		return -EINVAL;
 
 	iommu->dbg_cap_offset = dbg_cap_offset;