linux-stable.git/fs/fuse, branch linux-5.4.y

fuse: prevent overflow in copy_file_range return value

2025-10-02T11:34:28+00:00

commit 1e08938c3694f707bb165535df352ac97a8c75c9 upstream.

The FUSE protocol uses struct fuse_write_out to convey the return value of
copy_file_range, which is restricted to uint32_t.  But the COPY_FILE_RANGE
interface supports a 64-bit size copies.

Currently the number of bytes copied is silently truncated to 32-bit, which
may result in poor performance or even failure to copy in case of
truncation to zero.

Reported-by: Florian Weimer 
Closes: https://lore.kernel.org/all/lhuh5ynl8z5.fsf@oldenburg.str.redhat.com/
Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()")
Cc:  # v4.20
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: check if copy_file_range() returns larger than requested size

2025-10-02T11:34:28+00:00

commit e5203209b3935041dac541bc5b37efb44220cc0b upstream.

Just like write(), copy_file_range() should check if the return value is
less or equal to the requested number of bytes.

Reported-by: Chunsheng Luo 
Closes: https://lore.kernel.org/all/20250807062425.694-1-luochunsheng@ustc.edu/
Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()")
Cc:  # v4.20
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

virtiofs: add filesystem context source name check

2025-05-02T05:39:21+00:00

commit a94fd938df2b1628da66b498aa0eeb89593bc7a2 upstream.

In certain scenarios, for example, during fuzz testing, the source
name may be NULL, which could lead to a kernel panic. Therefore, an
extra check for the source name should be added.

Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem")
Cc:  # all LTS kernels
Signed-off-by: Xiangsheng Hou 
Link: https://lore.kernel.org/20250407115111.25535-1-xiangsheng.hou@mediatek.com
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

fuse: don't truncate cached, mutated symlink

2025-04-10T12:29:36+00:00

[ Upstream commit b4c173dfbb6c78568578ff18f9e8822d7bd0e31b ]

Fuse allows the value of a symlink to change and this property is exploited
by some filesystems (e.g. CVMFS).

It has been observed, that sometimes after changing the symlink contents,
the value is truncated to the old size.

This is caused by fuse_getattr() racing with fuse_reverse_inval_inode().
fuse_reverse_inval_inode() updates the fuse_inode's attr_version, which
results in fuse_change_attributes() exiting before updating the cached
attributes

This is okay, as the cached attributes remain invalid and the next call to
fuse_change_attributes() will likely update the inode with the correct
values.

The reason this causes problems is that cached symlinks will be
returned through page_get_link(), which truncates the symlink to
inode->i_size.  This is correct for filesystems that don't mutate
symlinks, but in this case it causes bad behavior.

The solution is to just remove this truncation.  This can cause a
regression in a filesystem that relies on supplying a symlink larger than
the file size, but this is unlikely.  If that happens we'd need to make
this behavior conditional.

Reported-by: Laura Promberger 
Tested-by: Sam Lewis 
Signed-off-by: Miklos Szeredi 
Link: https://lore.kernel.org/r/20250220100258.793363-1-mszeredi@redhat.com
Reviewed-by: Bernd Schubert 
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

fuse: use unsigned type for getxattr/listxattr size truncation

2024-09-12T09:03:51+00:00

commit b18915248a15eae7d901262f108d6ff0ffb4ffc1 upstream.

The existing code uses min_t(ssize_t, outarg.size, XATTR_LIST_MAX) when
parsing the FUSE daemon's response to a zero-length getxattr/listxattr
request.
On 32-bit kernels, where ssize_t and outarg.size are the same size, this is
wrong: The min_t() will pass through any size values that are negative when
interpreted as signed.
fuse_listxattr() will then return this userspace-supplied negative value,
which callers will treat as an error value.

This kind of bug pattern can lead to fairly bad security bugs because of
how error codes are used in the Linux kernel. If a caller were to convert
the numeric error into an error pointer, like so:

    struct foo *func(...) {
      int len = fuse_getxattr(..., NULL, 0);
      if (len < 0)
        return ERR_PTR(len);
      ...
    }

then it would end up returning this userspace-supplied negative value cast
to a pointer - but the caller of this function wouldn't recognize it as an
error pointer (IS_ERR_VALUE() only detects values in the narrow range in
which legitimate errno values are), and so it would just be treated as a
kernel pointer.

I think there is at least one theoretical codepath where this could happen,
but that path would involve virtio-fs with submounts plus some weird
SELinux configuration, so I think it's probably not a concern in practice.

Cc: stable@vger.kernel.org # v4.9
Fixes: 63401ccdb2ca ("fuse: limit xattr returned size")
Signed-off-by: Jann Horn 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: update stats for pages in dropped aux writeback list

2024-09-12T09:03:51+00:00

commit f7790d67785302b3116bbbfda62a5a44524601a3 upstream.

In the case where the aux writeback list is dropped (e.g. the pages
have been truncated or the connection is broken), the stats for
its pages and backing device info need to be updated as well.

Fixes: e2653bd53a98 ("fuse: fix leaked aux requests")
Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Cc:  # v5.1
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

virtiofs: forbid newlines in tags

2024-09-04T11:14:55+00:00

[ Upstream commit 40488cc16f7ea0d193a4e248f0d809c25cc377db ]

Newlines in virtiofs tags are awkward for users and potential vectors
for string injection attacks.

Signed-off-by: Stefan Hajnoczi 
Reviewed-by: Vivek Goyal 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

fuse: Initialize beyond-EOF page contents before setting uptodate

2024-09-04T11:14:49+00:00

commit 3c0da3d163eb32f1f91891efaade027fa9b245b9 upstream.

fuse_notify_store(), unlike fuse_do_readpage(), does not enable page
zeroing (because it can be used to change partial page contents).

So fuse_notify_store() must be more careful to fully initialize page
contents (including parts of the page that are beyond end-of-file)
before marking the page uptodate.

The current code can leave beyond-EOF page contents uninitialized, which
makes these uninitialized page contents visible to userspace via mmap().

This is an information leak, but only affects systems which do not
enable init-on-alloc (via CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y or the
corresponding kernel command line parameter).

Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2574
Cc: stable@kernel.org
Fixes: a1d75f258230 ("fuse: add store request")
Signed-off-by: Jann Horn 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

fuse: don't unhash root

2024-04-13T10:51:25+00:00

[ Upstream commit b1fe686a765e6c0d71811d825b5a1585a202b777 ]

The root inode is assumed to be always hashed.  Do not unhash the root
inode even if it is marked BAD.

Fixes: 5d069dbe8aaf ("fuse: fix bad inode")
Cc:  # v5.11
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

fuse: nlookup missing decrement in fuse_direntplus_link

2023-09-23T09:00:00+00:00

commit b8bd342d50cbf606666488488f9fea374aceb2d5 upstream.

During our debugging of glusterfs, we found an Assertion failed error:
inode_lookup >= nlookup, which was caused by the nlookup value in the
kernel being greater than that in the FUSE file system.

The issue was introduced by fuse_direntplus_link, where in the function,
fuse_iget increments nlookup, and if d_splice_alias returns failure,
fuse_direntplus_link returns failure without decrementing nlookup
https://github.com/gluster/glusterfs/pull/4081

Signed-off-by: ruanmeisi 
Fixes: 0b05b18381ee ("fuse: implement NFS-like readdirplus support")
Cc:  # v3.9
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman