commit 0bb99f2cfaae6822d734d69722de30af823efdf3 upstream.
Currently predictor flush on memory reuse is done for all BPF JIT
allocations, but only cBPF programs can be loaded by an unprivileged user.
eBPF is privileged by default, and flushing predictors for all CPUs on
every eBPF reuse penalizes the common case for no security benefit.
eBPF allocations can be frequent on busy systems, only flush predictors
for cBPF programs. Trampoline and dispatcher allocations also skip the
flush as they are eBPF-only.
[pawan: backport dropped "was_classic" hunk for arches that do not
support pack allocator]
Signed-off-by: Pawan Gupta <[email protected]>
Acked-by: Daniel Borkmann <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
---
arch/arm64/net/bpf_jit_comp.c | 4 ++--
arch/powerpc/net/bpf_jit_comp.c | 2 +-
arch/riscv/net/bpf_jit_comp64.c | 2 +-
arch/riscv/net/bpf_jit_core.c | 3 ++-
arch/x86/net/bpf_jit_comp.c | 5 +++--
include/linux/filter.h | 5 +++--
kernel/bpf/core.c | 13 ++++++++-----
kernel/bpf/dispatcher.c | 2 +-
8 files changed, 21 insertions(+), 15 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index c852749405e0..738e56b48f2a 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1881,7 +1881,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog
*prog)
image_size = extable_offset + extable_size;
ro_header = bpf_jit_binary_pack_alloc(image_size, &ro_image_ptr,
sizeof(u64), &header, &image_ptr,
- jit_fill_hole);
+ jit_fill_hole, was_classic);
if (!ro_header) {
prog = orig_prog;
goto out_off;
@@ -2413,7 +2413,7 @@ int arch_bpf_trampoline_size(const struct btf_func_model
*m, u32 flags,
void *arch_alloc_bpf_trampoline(unsigned int size)
{
- return bpf_prog_pack_alloc(size, jit_fill_hole);
+ return bpf_prog_pack_alloc(size, jit_fill_hole, false);
}
void arch_free_bpf_trampoline(void *image, unsigned int size)
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 55c3b64a5f3a..180175e072ad 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -174,7 +174,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len;
fhdr = bpf_jit_binary_pack_alloc(alloclen, &fimage, 4, &hdr, &image,
- bpf_jit_fill_ill_insns);
+ bpf_jit_fill_ill_insns,
bpf_prog_was_classic(fp));
if (!fhdr) {
fp = org_fp;
goto out_addrs;
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 5895c1b2be20..43a58e5e123f 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1113,7 +1113,7 @@ int arch_bpf_trampoline_size(const struct btf_func_model
*m, u32 flags,
void *arch_alloc_bpf_trampoline(unsigned int size)
{
- return bpf_prog_pack_alloc(size, bpf_fill_ill_insns);
+ return bpf_prog_pack_alloc(size, bpf_fill_ill_insns, false);
}
void arch_free_bpf_trampoline(void *image, unsigned int size)
diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
index 6de753c667f4..2f2af89ab4df 100644
--- a/arch/riscv/net/bpf_jit_core.c
+++ b/arch/riscv/net/bpf_jit_core.c
@@ -126,7 +126,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
bpf_jit_binary_pack_alloc(prog_size +
extable_size,
&jit_data->ro_image,
sizeof(u32),
&jit_data->header,
&jit_data->image,
- bpf_fill_ill_insns);
+ bpf_fill_ill_insns,
+
bpf_prog_was_classic(prog));
if (!jit_data->ro_header) {
prog = orig_prog;
goto out_offset;
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 8cbc26081bdb..4304596c8fdd 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -3206,7 +3206,7 @@ static int __arch_prepare_bpf_trampoline(struct
bpf_tramp_image *im, void *rw_im
void *arch_alloc_bpf_trampoline(unsigned int size)
{
- return bpf_prog_pack_alloc(size, jit_fill_hole);
+ return bpf_prog_pack_alloc(size, jit_fill_hole, false);
}
void arch_free_bpf_trampoline(void *image, unsigned int size)
@@ -3491,7 +3491,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog
*prog)
/* allocate module memory for x86 insns and extable */
header = bpf_jit_binary_pack_alloc(roundup(proglen,
align) + extable_size,
&image, align,
&rw_header, &rw_image,
- jit_fill_hole);
+ jit_fill_hole,
+
bpf_prog_was_classic(prog));
if (!header) {
prog = orig_prog;
goto out_addrs;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 8046cd2a39c6..b88a213bcbbe 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1262,7 +1262,7 @@ void bpf_jit_free(struct bpf_prog *fp);
struct bpf_binary_header *
bpf_jit_binary_pack_hdr(const struct bpf_prog *fp);
-void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns);
+void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns,
bool was_classic);
void bpf_prog_pack_free(void *ptr, u32 size);
static inline bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp)
@@ -1276,7 +1276,8 @@ bpf_jit_binary_pack_alloc(unsigned int proglen, u8
**ro_image,
unsigned int alignment,
struct bpf_binary_header **rw_hdr,
u8 **rw_image,
- bpf_jit_fill_hole_t bpf_fill_ill_insns);
+ bpf_jit_fill_hole_t bpf_fill_ill_insns,
+ bool was_classic);
int bpf_jit_binary_pack_finalize(struct bpf_binary_header *ro_header,
struct bpf_binary_header *rw_header);
void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 5f676320c53b..29d39092c457 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -952,7 +952,7 @@ static struct bpf_prog_pack
*alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_ins
return NULL;
}
-void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns)
+void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns,
bool was_classic)
{
unsigned int nbits = BPF_PROG_SIZE_TO_NBITS(size);
struct bpf_prog_pack *pack;
@@ -967,7 +967,7 @@ void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t
bpf_fill_ill_insns)
* safe because cBPF programs (the unprivileged attack surface)
* are bounded well below a pack size.
*/
- if (static_branch_unlikely(&bpf_pred_flush_enabled))
+ if (was_classic &&
static_branch_unlikely(&bpf_pred_flush_enabled))
pr_warn_once("BPF: Predictors not flushed for
allocations greater than BPF_PROG_PACK_SIZE\n");
size = round_up(size, PAGE_SIZE);
ptr = bpf_jit_alloc_exec(size);
@@ -999,7 +999,9 @@ void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t
bpf_fill_ill_insns)
pos = 0;
found_free_area:
- static_call_cond(bpf_arch_pred_flush)();
+ /* Flush only for cBPF as it may contain a crafted gadget */
+ if (static_branch_unlikely(&bpf_pred_flush_enabled) && was_classic)
+ static_call_cond(bpf_arch_pred_flush)();
bitmap_set(pack->bitmap, pos, nbits);
ptr = (void *)(pack->ptr) + (pos << BPF_PROG_CHUNK_SHIFT);
@@ -1159,7 +1161,8 @@ bpf_jit_binary_pack_alloc(unsigned int proglen, u8
**image_ptr,
unsigned int alignment,
struct bpf_binary_header **rw_header,
u8 **rw_image,
- bpf_jit_fill_hole_t bpf_fill_ill_insns)
+ bpf_jit_fill_hole_t bpf_fill_ill_insns,
+ bool was_classic)
{
struct bpf_binary_header *ro_header;
u32 size, hole, start;
@@ -1172,7 +1175,7 @@ bpf_jit_binary_pack_alloc(unsigned int proglen, u8
**image_ptr,
if (bpf_jit_charge_modmem(size))
return NULL;
- ro_header = bpf_prog_pack_alloc(size, bpf_fill_ill_insns);
+ ro_header = bpf_prog_pack_alloc(size, bpf_fill_ill_insns, was_classic);
if (!ro_header) {
bpf_jit_uncharge_modmem(size);
return NULL;
diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c
index b77db7413f8c..ea2d60dc1fee 100644
--- a/kernel/bpf/dispatcher.c
+++ b/kernel/bpf/dispatcher.c
@@ -145,7 +145,7 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d,
struct bpf_prog *from,
mutex_lock(&d->mutex);
if (!d->image) {
- d->image = bpf_prog_pack_alloc(PAGE_SIZE,
bpf_jit_fill_hole_with_zero);
+ d->image = bpf_prog_pack_alloc(PAGE_SIZE,
bpf_jit_fill_hole_with_zero, false);
if (!d->image)
goto out;
d->rw_image = bpf_jit_alloc_exec(PAGE_SIZE);
--
2.43.0
