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git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
synced 2026-10-28 04:45:43 +01:00
Christian Brauner
56c3824de5
ntfs_fs_reconfigure() replaces the old mount options with new mount
options in sbi->options. The old mount options land in fs_context and
are freed as soon as remount returns. With a pathwalk held up in
ntfs_nls_to_utf16() between loading sbi->options and dereferencing it
while a remount replaces them:
BUG: KASAN: slab-use-after-free in ntfs_nls_to_utf16+0x7ae/0x7c0
Read of size 8 at addr ff110001044fd448 by task walker/98
Call Trace:
<TASK>
ntfs_nls_to_utf16+0x7ae/0x7c0
ntfs_d_hash+0x22b/0x500
link_path_walk+0x11ad/0x1d30
path_lookupat+0x63/0xb00
filename_lookup+0x1f1/0x5b0
vfs_statx+0xd7/0x3b0
[...]
Allocated by task 95:
__kmalloc_node_track_caller_noprof+0x2a2/0x730
kmemdup_noprof+0x25/0x50
ntfs_fill_super+0x1e5/0x4550
[...]
Freed by task 97:
kfree+0x1db/0x5b0
put_fs_context+0x13c/0x7d0
path_mount+0x54a/0x2130
__x64_sys_mount+0x20c/0x270
That info is needed in rcu lookup in the dentry hash and dentry compary
methods for ntfs3 and causes a UAF today. Delay freeing with an rcu
grace period.
ntfs_nls_to_utf16() reads ->nls and ->ads once under rcu_read_lock() so
the hooks pair with the release in ntfs_fs_reconfigure(). That also
covers callers outside of rcu pathwalk such as ntfs_lookup(). They don't
hold rcu_read_lock() themselves and wouldn't be protected by the grace
period otherwise. Remount refuses to change the iocharset so ->nls stays
valid after rcu_read_unlock().
Fixes: a3a956c78e ("fs/ntfs3: Add option "nocase"")
Cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Christian Brauner (Amutable) <[email protected]>