diff mbox series

[v4,bpf-next,03/10] bpf: fix check for attempt to corrupt spilled pointer

Message ID 20231205184248.1502704-4-andrii@kernel.org (mailing list archive)
State Accepted
Commit ab125ed3ec1c10ccc36bc98c7a4256ad114a3dae
Delegated to: BPF
Headers show
Series Complete BPF verifier precision tracking support for register spills | expand

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netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/ynl success SINGLE THREAD; Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1127 this patch: 1127
netdev/cc_maintainers fail 1 blamed authors not CCed: martin.lau@linux.dev; 8 maintainers not CCed: kpsingh@kernel.org sdf@google.com yonghong.song@linux.dev martin.lau@linux.dev song@kernel.org haoluo@google.com jolsa@kernel.org john.fastabend@gmail.com
netdev/build_clang success Errors and warnings before: 1147 this patch: 1147
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netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 1154 this patch: 1154
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netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-PR success PR summary

Commit Message

Andrii Nakryiko Dec. 5, 2023, 6:42 p.m. UTC 
When register is spilled onto a stack as a 1/2/4-byte register, we set
slot_type[BPF_REG_SIZE - 1] (plus potentially few more below it,
depending on actual spill size). So to check if some stack slot has
spilled register we need to consult slot_type[7], not slot_type[0].

To avoid the need to remember and double-check this in the future, just
use is_spilled_reg() helper.

Fixes: 27113c59b6d0 ("bpf: Check the other end of slot_type for STACK_SPILL")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9bc16dc66465..3edca06de9fd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4431,7 +4431,7 @@  static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 	 * so it's aligned access and [off, off + size) are within stack limits
 	 */
 	if (!env->allow_ptr_leaks &&
-	    state->stack[spi].slot_type[0] == STACK_SPILL &&
+	    is_spilled_reg(&state->stack[spi]) &&
 	    size != BPF_REG_SIZE) {
 		verbose(env, "attempt to corrupt spilled pointer on stack\n");
 		return -EACCES;