lkml.org 
[lkml]   [2018]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] bpf: prevent memory disambiguation attack
From
Date
On 05/21/2018 11:17 PM, Alexei Starovoitov wrote:
> Detect code patterns where malicious 'speculative store bypass' can be used
> and sanitize such patterns.
>
> 39: (bf) r3 = r10
> 40: (07) r3 += -216
> 41: (79) r8 = *(u64 *)(r7 +0) // slow read
> 42: (7a) *(u64 *)(r10 -72) = 0 // verifier inserts this instruction
> 43: (7b) *(u64 *)(r8 +0) = r3 // this store becomes slow due to r8
> 44: (79) r1 = *(u64 *)(r6 +0) // cpu speculatively executes this load
> 45: (71) r2 = *(u8 *)(r1 +0) // speculatively arbitrary 'load byte'
> // is now sanitized
>
> Above code after x86 JIT becomes:
> e5: mov %rbp,%rdx
> e8: add $0xffffffffffffff28,%rdx
> ef: mov 0x0(%r13),%r14
> f3: movq $0x0,-0x48(%rbp)
> fb: mov %rdx,0x0(%r14)
> ff: mov 0x0(%rbx),%rdi
> 103: movzbq 0x0(%rdi),%rsi
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

(No further action needed since already in Linus tree [1]. This went via the
batch of x86 fixes on the speculative store buffer bypass from today [2].)

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=af86ca4e3088fe5eacf2f7e58c01fa68ca067672
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3b78ce4a34b761c7fe13520de822984019ff1a8f

\
 
 \ /
  Last update: 2018-05-21 23:46    [W:0.039 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site