dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel()grafted

When dma_device_put() drops the last reference on chan->device->ref,
dma_device_release() runs and may free the dma_device along with its
channels.

dma_chan_put() then still reads chan->device->owner via
dma_chan_to_owner() for the trailing module_put(). KASAN catches it:

	slab-use-after-free in dma_chan_put+0x3e6/0x4c0
	Read of size 8 by task insmod/6319
	Freed by task 6319:
	  kfree+0x225/0x470
	  dma_chan_put+0x395/0x4c0
	  dmaengine_put+0xf8/0x160

Cache the module owner in dma_chan_put() before the put so the trailing
module_put() does not need chan->device.

Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 50 insertions, 0 deletions

diff --git a/fs/ext2/Kconfig b/fs/ext2/Kconfig
new file mode 100644
index 000000000..d5bce83ad
--- /dev/null
+++ b/fs/ext2/Kconfig
@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config EXT2_FS
+	tristate "Second extended fs support (DEPRECATED)"
+	select BUFFER_HEAD
+	select FS_IOMAP
+	help
+	  Ext2 is a standard Linux file system for hard disks.
+
+	  This filesystem driver is deprecated because it does not properly
+	  support inode time stamps beyond 03:14:07 UTC on 19 January 2038.
+
+	  Ext2 users are advised to use ext4 driver to access their filesystem.
+	  The driver is fully compatible, supports filesystems without journal
+          or extents, and also supports larger time stamps if the filesystem
+          is created with at least 256 byte inodes.
+
+	  This code is kept as a simple reference for filesystem developers.
+
+	  If unsure, say N.
+
+config EXT2_FS_XATTR
+	bool "Ext2 extended attributes"
+	depends on EXT2_FS
+	help
+	  Extended attributes are name:value pairs associated with inodes by
+	  the kernel or by users (see the attr(5) manual page for details).
+
+	  If unsure, say N.
+
+config EXT2_FS_POSIX_ACL
+	bool "Ext2 POSIX Access Control Lists"
+	depends on EXT2_FS_XATTR
+	select FS_POSIX_ACL
+	help
+	  Posix Access Control Lists (ACLs) support permissions for users and
+	  groups beyond the owner/group/world scheme.
+
+	  If you don't know what Access Control Lists are, say N
+
+config EXT2_FS_SECURITY
+	bool "Ext2 Security Labels"
+	depends on EXT2_FS_XATTR
+	help
+	  Security labels support alternative access control models
+	  implemented by security modules like SELinux.  This option
+	  enables an extended attribute handler for file security
+	  labels in the ext2 filesystem.
+
+	  If you are not using a security module that requires using
+	  extended attributes for file security labels, say N.