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author | Kees Cook <keescook@chromium.org> | 2019-06-22 23:18:23 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-23 08:05:56 +0300 |
commit | 06b32fdb030989c45bb9dad685b794bf2395d53a (patch) | |
tree | c73030b5bb87d2923868488574fbd3bf2093046c /drivers/i2c/busses/i2c-simtec.c | |
parent | 1909a671dbc3606685b1daf8b22a16f65ea7edda (diff) | |
download | linux-06b32fdb030989c45bb9dad685b794bf2395d53a.tar.xz |
lkdtm: Check for SMEP clearing protections
This adds an x86-specific test for pinned cr4 bits. A successful test
will validate pinning and check the ROP-style call-middle-of-function
defense, if needed. For example, in the case of native_write_cr4()
looking like this:
ffffffff8171bce0 <native_write_cr4>:
ffffffff8171bce0: 48 8b 35 79 46 f2 00 mov 0xf24679(%rip),%rsi
ffffffff8171bce7: 48 09 f7 or %rsi,%rdi
ffffffff8171bcea: 0f 22 e7 mov %rdi,%cr4
...
ffffffff8171bd5a: c3 retq
The UNSET_SMEP test will jump to ffffffff8171bcea (the mov to cr4)
instead of ffffffff8171bce0 (native_write_cr4() entry) to simulate a
direct-call bypass attempt.
Expected successful results:
# echo UNSET_SMEP > /sys/kernel/debug/provoke-crash/DIRECT
# dmesg
[ 79.594433] lkdtm: Performing direct entry UNSET_SMEP
[ 79.596459] lkdtm: trying to clear SMEP normally
[ 79.598406] lkdtm: ok: SMEP did not get cleared
[ 79.599981] lkdtm: trying to clear SMEP with call gadget
[ 79.601810] ------------[ cut here ]------------
[ 79.603421] Attempt to unpin cr4 bits: 100000; bypass attack?!
...
[ 79.650170] ---[ end trace 2452ca0f6126242e ]---
[ 79.650937] lkdtm: ok: SMEP removal was reverted
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/i2c/busses/i2c-simtec.c')
0 files changed, 0 insertions, 0 deletions