[PATCH AUTOSEL 5.7 271/274] s390/bpf: Maintain 8-byte stack alignment

Sasha Levin
2020-06-09T00:44:06Z

From: Ilya Leoshkevich <iii@linux.ibm.com>

[ Upstream commit effe5be17706167ee968fa28afe40dec9c6f71db ]

Certain kernel functions (e.g. get_vtimer/set_vtimer) cause kernel
panic when the stack is not 8-byte aligned. Currently JITed BPF programs
may trigger this by allocating stack frames with non-rounded sizes and
then being interrupted. Fix by using rounded fp->aux->stack_depth.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200602174339.2501066-1-iii@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/net/bpf_jit_comp.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 8d2134136290..0f37a1b635f8 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -594,7 +594,7 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
* stack space for the large switch statement.
*/
static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
- int i, bool extra_pass)
+ int i, bool extra_pass, u32 stack_depth)
{
struct bpf_insn *insn = &fp->insnsi[i];
u32 dst_reg = insn->dst_reg;
@@ -1207,7 +1207,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
*/

if (jit->seen & SEEN_STACK)
- off = STK_OFF_TCCNT + STK_OFF + fp->aux->stack_depth;
+ off = STK_OFF_TCCNT + STK_OFF + stack_depth;
else
off = STK_OFF_TCCNT;
/* lhi %w0,1 */
@@ -1249,7 +1249,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
/*
* Restore registers before calling function
*/
- save_restore_regs(jit, REGS_RESTORE, fp->aux->stack_depth);
+ save_restore_regs(jit, REGS_RESTORE, stack_depth);

/*
* goto *(prog->bpf_func + tail_call_start);
@@ -1519,7 +1519,7 @@ static int bpf_set_addr(struct bpf_jit *jit, int i)
* Compile eBPF program into s390x code
*/
static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
- bool extra_pass)
+ bool extra_pass, u32 stack_depth)
{
int i, insn_count, lit32_size, lit64_size;

@@ -1527,18 +1527,18 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
jit->lit64 = jit->lit64_start;
jit->prg = 0;

- bpf_jit_prologue(jit, fp->aux->stack_depth);
+ bpf_jit_prologue(jit, stack_depth);
if (bpf_set_addr(jit, 0) < 0)
return -1;
for (i = 0; i < fp->len; i += insn_count) {
- insn_count = bpf_jit_insn(jit, fp, i, extra_pass);
+ insn_count = bpf_jit_insn(jit, fp, i, extra_pass, stack_depth);
if (insn_count < 0)
return -1;
/* Next instruction address */
if (bpf_set_addr(jit, i + insn_count) < 0)
return -1;
}
- bpf_jit_epilogue(jit, fp->aux->stack_depth);
+ bpf_jit_epilogue(jit, stack_depth);

lit32_size = jit->lit32 - jit->lit32_start;
lit64_size = jit->lit64 - jit->lit64_start;
@@ -1569,6 +1569,7 @@ struct s390_jit_data {
*/
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
{
+ u32 stack_depth = round_up(fp->aux->stack_depth, 8);
struct bpf_prog *tmp, *orig_fp = fp;
struct bpf_binary_header *header;
struct s390_jit_data *jit_data;
@@ -1621,7 +1622,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
* - 3: Calculate program size and addrs arrray
*/
for (pass = 1; pass <= 3; pass++) {
- if (bpf_jit_prog(&jit, fp, extra_pass)) {
+ if (bpf_jit_prog(&jit, fp, extra_pass, stack_depth)) {
fp = orig_fp;
goto free_addrs;
}
@@ -1635,7 +1636,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
goto free_addrs;
}
skip_init_ctx:
- if (bpf_jit_prog(&jit, fp, extra_pass)) {
+ if (bpf_jit_prog(&jit, fp, extra_pass, stack_depth)) {
bpf_jit_binary_free(header);
fp = orig_fp;
goto free_addrs;
--
2.25.1