[PATCH v2025.09.y 31/58] FIT: fix potential underflow of stack array

[Ahmad Fatoum]

Add a bounds check on depth before decrementing to prevent
stack underflow when a malformed FDT has END_NODE before BEGIN_NODE.

(cherry picked from commit 38ee3bd662a87ed0d54d2f8646d90130e2d5d11a)

Reported-by: clang-analyzer 19.1.7
Co-Authored-By: Claude Opus 4.6 <noreply at anthropic.com>
Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
Link: https://lore.barebox.org/20260216084142.3546363-2-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 common/image-fit.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/common/image-fit.c b/common/image-fit.c
index 027b268928d3..9748e5f1d8f0 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -153,6 +153,8 @@ static int fit_digest(struct fit_handle *handle, struct digest *digest,
 		case FDT_END_NODE:
 			dt_struct = dt_struct_advance(&f, dt_struct, FDT_TAGSIZE);
 
+			if (depth < 0)
+				return -ESPIPE;
 			include = want;
 			want = stack[depth--];
 			while (end > path && *--end != '/')
-- 
2.47.3