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/nfsd/debugfs.c | 147 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 147 insertions(+) create mode 100644 fs/nfsd/debugfs.c (limited to 'fs/nfsd/debugfs.c') diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c new file mode 100644 index 000000000..386fd1c54 --- /dev/null +++ b/fs/nfsd/debugfs.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +#include "nfsd.h" + +static struct dentry *nfsd_top_dir __read_mostly; + +/* + * /sys/kernel/debug/nfsd/disable-splice-read + * + * Contents: + * %0: NFS READ is allowed to use page splicing + * %1: NFS READ uses only iov iter read + * + * The default value of this setting is zero (page splicing is + * allowed). This setting takes immediate effect for all NFS + * versions, all exports, and in all NFSD net namespaces. + */ + +static int nfsd_dsr_get(void *data, u64 *val) +{ + *val = nfsd_disable_splice_read ? 1 : 0; + return 0; +} + +static int nfsd_dsr_set(void *data, u64 val) +{ + nfsd_disable_splice_read = (val > 0); + if (!nfsd_disable_splice_read) { + /* + * Must use buffered I/O if splice_read is enabled. + */ + nfsd_io_cache_read = NFSD_IO_BUFFERED; + } + return 0; +} + +DEFINE_DEBUGFS_ATTRIBUTE(nfsd_dsr_fops, nfsd_dsr_get, nfsd_dsr_set, "%llu\n"); + +/* + * /sys/kernel/debug/nfsd/io_cache_read + * + * Contents: + * %0: NFS READ will use buffered IO + * %1: NFS READ will use dontcache (buffered IO w/ dropbehind) + * %2: NFS READ will use direct IO + * + * This setting takes immediate effect for all NFS versions, + * all exports, and in all NFSD net namespaces. + */ + +static int nfsd_io_cache_read_get(void *data, u64 *val) +{ + *val = nfsd_io_cache_read; + return 0; +} + +static int nfsd_io_cache_read_set(void *data, u64 val) +{ + int ret = 0; + + switch (val) { + case NFSD_IO_BUFFERED: + nfsd_io_cache_read = NFSD_IO_BUFFERED; + break; + case NFSD_IO_DONTCACHE: + case NFSD_IO_DIRECT: + /* + * Must disable splice_read when enabling + * NFSD_IO_DONTCACHE. + */ + nfsd_disable_splice_read = true; + nfsd_io_cache_read = val; + break; + default: + ret = -EINVAL; + break; + } + + return ret; +} + +DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get, + nfsd_io_cache_read_set, "%llu\n"); + +/* + * /sys/kernel/debug/nfsd/io_cache_write + * + * Contents: + * %0: NFS WRITE will use buffered IO + * %1: NFS WRITE will use dontcache (buffered IO w/ dropbehind) + * + * This setting takes immediate effect for all NFS versions, + * all exports, and in all NFSD net namespaces. + */ + +static int nfsd_io_cache_write_get(void *data, u64 *val) +{ + *val = nfsd_io_cache_write; + return 0; +} + +static int nfsd_io_cache_write_set(void *data, u64 val) +{ + int ret = 0; + + switch (val) { + case NFSD_IO_BUFFERED: + case NFSD_IO_DONTCACHE: + case NFSD_IO_DIRECT: + nfsd_io_cache_write = val; + break; + default: + ret = -EINVAL; + break; + } + + return ret; +} + +DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_write_fops, nfsd_io_cache_write_get, + nfsd_io_cache_write_set, "%llu\n"); + +void nfsd_debugfs_exit(void) +{ + debugfs_remove_recursive(nfsd_top_dir); + nfsd_top_dir = NULL; +} + +void nfsd_debugfs_init(void) +{ + nfsd_top_dir = debugfs_create_dir("nfsd", NULL); + + debugfs_create_file("disable-splice-read", S_IWUSR | S_IRUGO, + nfsd_top_dir, NULL, &nfsd_dsr_fops); + + debugfs_create_file("io_cache_read", 0644, nfsd_top_dir, NULL, + &nfsd_io_cache_read_fops); + + debugfs_create_file("io_cache_write", 0644, nfsd_top_dir, NULL, + &nfsd_io_cache_write_fops); +#ifdef CONFIG_NFSD_V4 + debugfs_create_bool("delegated_timestamps", 0644, nfsd_top_dir, + &nfsd_delegts_enabled); +#endif +} -- cgit v1.3.1