ext4: avoid use-after-free in ext4_ext_show_leaf()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ext4: avoid use-after-free in ext4_ext_show_leaf() In ext4_find_extent(), path may be freed by error or be reallocated, so using a previously saved *ppath may have been freed and thus may trigger use-after-free, as follows: ext4_split_extent path = *ppath; ext4_split_extent_at(ppath) path = ext4_find_extent(ppath) ext4_split_extent_at(ppath) // ext4_find_extent fails to free path // but zeroout succeeds ext4_ext_show_leaf(inode, path) eh = path[depth].p_hdr // path use-after-free !!! Similar to ext4_split_extent_at(), we use *ppath directly as an input to ext4_ext_show_leaf(). Fix a spelling error by the way. Same problem in ext4_ext_handle_unwritten_extents(). Since 'path' is only used in ext4_ext_show_leaf(), remove 'path' and use *ppath directly. This issue is triggered only when EXT_DEBUG is defined and therefore does not affect functionality.

References

• https://git.kernel.org/stable/c/b0cb4561fc4284d04e69c8a66c8504928ab2484e
• https://git.kernel.org/stable/c/4999fed877bb64e3e7f9ab9996de2ca983c41928
• https://git.kernel.org/stable/c/2eba3b0cc5b8de624918d21f32b5b8db59a90b39
• https://git.kernel.org/stable/c/34b2096380ba475771971a778a478661a791aa15
• https://git.kernel.org/stable/c/8b114f2cc7dd5d36729d040b68432fbd0f0a8868
• https://git.kernel.org/stable/c/d483c7cc1796bd6a80e7b3a8fd494996260f6b67
• https://git.kernel.org/stable/c/4e2524ba2ca5f54bdbb9e5153bea00421ef653f5