From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001 From: Shivank Garg Date: Sat, 22 Aug 2026 19:22:05 +0000 Subject: dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() 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 Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Reviewed-by: Frank Li Reviewed-by: Logan Gunthorpe Signed-off-by: Shivank Garg Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com Signed-off-by: Vinod Koul --- fs/nullfs.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) create mode 100644 fs/nullfs.c (limited to 'fs/nullfs.c') diff --git a/fs/nullfs.c b/fs/nullfs.c new file mode 100644 index 000000000..e06352c7b --- /dev/null +++ b/fs/nullfs.c @@ -0,0 +1,66 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2026 Christian Brauner */ +#include +#include +#include + +#include "mount.h" + +static const struct super_operations nullfs_super_operations = { + .statfs = simple_statfs, +}; + +static int nullfs_fs_fill_super(struct super_block *s, struct fs_context *fc) +{ + struct inode *inode; + + s->s_maxbytes = MAX_LFS_FILESIZE; + s->s_blocksize = PAGE_SIZE; + s->s_blocksize_bits = PAGE_SHIFT; + s->s_magic = NULL_FS_MAGIC; + s->s_op = &nullfs_super_operations; + s->s_export_op = NULL; + s->s_xattr = NULL; + s->s_time_gran = 1; + s->s_d_flags = 0; + + inode = new_inode(s); + if (!inode) + return -ENOMEM; + + /* nullfs is permanently empty... */ + make_empty_dir_inode(inode); + simple_inode_init_ts(inode); + inode->i_ino = 1; + /* ... and immutable. */ + inode->i_flags |= S_IMMUTABLE; + + s->s_root = d_make_root(inode); + if (!s->s_root) + return -ENOMEM; + + return 0; +} + +static int nullfs_fs_get_tree(struct fs_context *fc) +{ + return get_tree_nodev(fc, nullfs_fs_fill_super); +} + +static const struct fs_context_operations nullfs_fs_context_ops = { + .get_tree = nullfs_fs_get_tree, +}; + +static int nullfs_init_fs_context(struct fs_context *fc) +{ + fc->ops = &nullfs_fs_context_ops; + fc->sb_flags |= SB_NOUSER; + fc->s_iflags |= SB_I_NOEXEC | SB_I_NODEV; + return 0; +} + +struct file_system_type nullfs_fs_type = { + .name = "nullfs", + .init_fs_context = nullfs_init_fs_context, + .kill_sb = kill_anon_super, +}; -- cgit v1.3.1