Description
If the vmwgfx driver fails to copy the 'fence_rep' object to userland, it tries to recover by deallocating the (already populated) file descriptor. This is wrong, as the fd gets released via put_unused_fd() which shouldn't be used, as the fd table slot was already populated via the previous call to fd_install(). This leaves userland with a valid fd table entry pointing to a free'd 'file' object.
We use this bug to overwrite a SUID binary with our payload and gain root. Linux kernel 4.14 - 5.16.x are vulnerable.
Successfully tested against Ubuntu 22.04.01 with kernel 5.13.12-051312-generic.
Module options
To display the available options, load the module within the Metasploit console and run the commands 'show options' or 'show advanced':
msf > use exploit/linux/local/vmwgfx/fd_priv_escmsf undefined(fd_priv_esc) > show actions ...actions...msf undefined(fd_priv_esc) > set ACTION < action-name >msf undefined(fd_priv_esc) > show options ...show and set options...msf undefined(fd_priv_esc) > runPrioritise with Active Threat Intelligence
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