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1a73f5b8f0
Following process:
P1 P2
path_lookupat
link_path_walk
inode_permission
ovl_permission
ovl_i_path_real(inode, &realpath)
path->dentry = ovl_i_dentry_upper(inode)
drop_cache
__dentry_kill(ovl_dentry)
iput(ovl_inode)
ovl_destroy_inode(ovl_inode)
dput(oi->__upperdentry)
dentry_kill(upperdentry)
dentry_unlink_inode
upperdentry->d_inode = NULL
realinode = d_inode(realpath.dentry) // return NULL
inode_permission(realinode)
inode->i_sb // NULL pointer dereference
, will trigger an null pointer dereference at realinode:
[ 335.664979] BUG: kernel NULL pointer dereference,
address: 0000000000000002
[ 335.668032] CPU: 0 PID: 2592 Comm: ls Not tainted 6.3.0
[ 335.669956] RIP: 0010:inode_permission+0x33/0x2c0
[ 335.678939] Call Trace:
[ 335.679165] <TASK>
[ 335.679371] ovl_permission+0xde/0x320
[ 335.679723] inode_permission+0x15e/0x2c0
[ 335.680090] link_path_walk+0x115/0x550
[ 335.680771] path_lookupat.isra.0+0xb2/0x200
[ 335.681170] filename_lookup+0xda/0x240
[ 335.681922] vfs_statx+0xa6/0x1f0
[ 335.682233] vfs_fstatat+0x7b/0xb0
Fetch a reproducer in [Link].
Use the helper ovl_i_path_realinode() to get realinode and then do
non-nullptr checking.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217405
Fixes: 4b7791b2e9 ("ovl: handle idmappings in ovl_permission()")
Cc: <stable@vger.kernel.org> # v5.19
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Suggested-by: Christian Brauner <brauner@kernel.org>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.