CVE-2025-38527

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free in cifs_oplock_break A race condition can occur in cifs_oplock_break() leading to a use-after-free of the cinode structure when unmounting: cifs_oplock_break() _cifsFileInfo_put(cfile) cifsFileInfo_put_final() cifs_sb_deactive() [last ref, start releasing sb] kill_sb() kill_anon_super() generic_shutdown_super() evict_inodes() dispose_list() evict() destroy_inode() call_rcu(&inode->i_rcu, i_callback) spin_lock(&cinode->open_file_lock) <- OK [later] i_callback() cifs_free_inode() kmem_cache_free(cinode) spin_unlock(&cinode->open_file_lock) <- UAF cifs_done_oplock_break(cinode) <- UAF The issue occurs when umount has already released its reference to the superblock. When _cifsFileInfo_put() calls cifs_sb_deactive(), this releases the last reference, triggering the immediate cleanup of all inodes under RCU. However, cifs_oplock_break() continues to access the cinode after this point, resulting in use-after-free. Fix this by holding an extra reference to the superblock during the entire oplock break operation. This ensures that the superblock and its inodes remain valid until the oplock break completes.

PUBLISHED Reserved 2025-04-16 | Published 2025-08-16 | Updated 2025-08-28 | Assigner Linux

Product status

References

git.kernel.org/...c/4256a483fe58af66a46cbf3dc48ff26e580d3308

git.kernel.org/...c/0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b

git.kernel.org/...c/2baaf5bbab2ac474c4f92c10fcb3310f824db995

git.kernel.org/...c/09bce2138a30ef10d8821c8c3f73a4ab7a5726bc

git.kernel.org/...c/da11bd4b697b393a207f19a2ed7d382a811a3ddc

git.kernel.org/...c/705c79101ccf9edea5a00d761491a03ced314210

cve.org (CVE-2025-38527)

nvd.nist.gov (CVE-2025-38527)

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