Commit 1f7bdea654 for ffmpeg

commit 1f7bdea654a8a9a1761759e22d83943371cff21f
Author: Michael Niedermayer <michael@niedermayer.cc>
Date:   Thu Oct 29 02:11:48 2026 +0100

    avcodec/riscv/llvidencdsp: return from diff_bytes for lengths of zero or less

    Heap corruption Replicated through UnModified FFmpeg with qemu-riscv64 (RVV)

    Fixes: heap corruption
    Fixes: CDfb2GDVrz5J
    Fixes: AISLE-2026-0150-00800

    Found-by: Joshua Rogers (AISLE)
    Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/riscv/llvidencdsp_rvv.S b/libavcodec/riscv/llvidencdsp_rvv.S
index 35ac976dd0..beedf21b75 100644
--- a/libavcodec/riscv/llvidencdsp_rvv.S
+++ b/libavcodec/riscv/llvidencdsp_rvv.S
@@ -22,6 +22,7 @@

 func ff_llvidenc_diff_bytes_rvv, zve32x
         lpad    0
+        blez    a3, 2f
 1:
         vsetvli t0, a3, e8, m8, ta, ma
         vle8.v  v0, (a1)
@@ -33,7 +34,7 @@ func ff_llvidenc_diff_bytes_rvv, zve32x
         vse8.v  v8, (a0)
         add     a0, t0, a0
         bnez    a3, 1b
-
+2:
         ret
 endfunc