diff options
| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2026-06-29 22:37:52 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2026-07-01 10:33:35 +0200 |
| commit | 96cce16e26dd02a8678f1e87f88a4b5cdb63b995 (patch) | |
| tree | 9cf15a2717185fbce3df83b7be82b1658ef043c7 /include | |
| parent | a6f0643e4f63cfaa0d5d4a69de4f132eac4b8fe4 (diff) | |
bpf: Support for hardening against JIT spraying
The BPF JIT allocator packs many small programs into larger executable
allocations and reuses space within those allocations as programs are
loaded and freed. When fresh code is written into space that a previous
program occupied, an indirect jump into the new program can reuse a branch
prediction left behind by the old one.
Flush the indirect branch predictors before reusing JIT memory so that
indirect jumps into a newly written program don't reuse predictions from an
old program that occupied the same space.
Introduce bpf_arch_pred_flush_enabled static key and bpf_arch_pred_flush
static call for flushing the branch predictors on JIT memory reuse.
Architectures that need a flush, can update it to a predictor flush
function. By default, its a NOP and does not emit any CALL.
Allocations larger than a pack are not covered by this flush. That is safe
because cBPF programs (the unprivileged attack surface) are bounded well
below a pack size. Issue a warning if this assumption is ever violated
while the flush is active.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/filter.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index 67d337ede91b..f68694f94ee7 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -21,6 +21,7 @@ #include <linux/if_vlan.h> #include <linux/vmalloc.h> #include <linux/sockptr.h> +#include <linux/static_call.h> #include <linux/u64_stats_sync.h> #include <net/sch_generic.h> @@ -1314,6 +1315,15 @@ extern long bpf_jit_limit_max; typedef void (*bpf_jit_fill_hole_t)(void *area, unsigned int size); +/* + * Flush the indirect branch predictors before reusing JIT memory, so that + * indirect jumps into a newly written program don't reuse predictions left + * behind by an old program that occupied the same space. + */ +void bpf_arch_pred_flush(void); +DECLARE_STATIC_CALL(bpf_arch_pred_flush, bpf_arch_pred_flush); +DECLARE_STATIC_KEY_FALSE(bpf_pred_flush_enabled); + void bpf_jit_fill_hole_with_zero(void *area, unsigned int size); struct bpf_binary_header * |