bpf: Disable file_alloc_security hook #6425
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A use-after-free bug may be triggered by calling bpf_inode_storage_get()
in a BPF LSM program hooked to file_alloc_security. Disable the hook to
prevent this from happening.
The cause of the bug is shown in the trace below. In alloc_file(), a
file struct is first allocated through kmem_cache_alloc(). Then,
file_alloc_security hook is invoked. Since the zero initialization or
assignment of f->f_inode happen after this LSM hook, a BPF program may
get a dangeld inode pointer by walking the file struct.
alloc_file()
-> alloc_empty_file()
-> f = kmem_cache_alloc()
-> init_file()
-> security_file_alloc() // f->f_inode not init-ed yet!
-> f->f_inode = NULL;
-> file_init_path()
-> f->f_inode = path->dentry->d_inode
Reported-by: Kaiyan Mei <[email protected]>
Reported-by: Yinhao Hu <[email protected]>
Reported-by: Dongliang Mu <[email protected]>
Closes: https://lore.kernel.org/bpf/[email protected]/
Signed-off-by: Amery Hung <[email protected]>
file_alloc_security hook is disabled. Use other LSM hooks in selftests instead. Signed-off-by: Amery Hung <[email protected]>
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Upstream branch: 688b745 |
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Pull request for series with
subject: bpf: Disable file_alloc_security hook
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1028029