[5.10][Bugfix] ceph: prevent use-after-free in encode_cap_msg() · Pull Request !3152 · anolis/cloud-kernel

bugzilla: https://bugzilla.openanolis.cn/show_bug.cgi?id=8998

In fs/ceph/caps.c, in encode_cap_msg(), "use after free" error was
caught by KASAN at this line - 'ceph_buffer_get(arg->xattr_buf);'. This
implies before the refcount could be increment here, it was freed.

In same file, in "handle_cap_grant()" refcount is decremented by this
line - 'ceph_buffer_put(ci->i_xattrs.blob);'. It appears that a race
occurred and resource was freed by the latter line before the former
line could increment it.

encode_cap_msg() is called by __send_cap() and __send_cap() is called by
ceph_check_caps() after calling __prep_cap(). __prep_cap() is where
arg->xattr_buf is assigned to ci->i_xattrs.blob. This is the spot where
the refcount must be increased to prevent "use after free" error.

patch from upstream

ceph: prevent use-after-free in encode_cap_msg()

commit	8180d0c27b93a6eb60da1b08ea079e3926328214

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.10.y&id=8180d0c27b93a6eb60da1b08ea079e3926328214

类型	指派人员	状态
审查	hsiangkao josephhz JeffleXu	已完成 (0/0人)
测试	小龙已测试通过	已完成 (1/1人)

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