Fix setjmp/longjump usage in JPEG error handling

Pushes and pops nested jmp_bufs in a stack for proper handling of
nested setjmp calls. Ensures longjmp is never called to a stack frame
that has exited.

Bug: skia:
Change-Id: I18d62504f6e5e3eb53026c3b48617b92ea74b905
Reviewed-on: https://skia-review.googlesource.com/79241
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/src/codec/SkJpegPriv.h b/src/codec/SkJpegPriv.h
index e4e5b12763..ce2da56225 100644
--- a/src/codec/SkJpegPriv.h
+++ b/src/codec/SkJpegPriv.h
@@ -10,6 +10,7 @@
 #define SkJpegPriv_DEFINED
 
 #include "SkStream.h"
+#include "SkTArray.h"
 
 #include <setjmp.h>
 // stdio is needed for jpeglib
@@ -30,7 +31,23 @@ static constexpr uint8_t kICCSig[] = {
  * Error handling struct
  */
 struct skjpeg_error_mgr : jpeg_error_mgr {
-    jmp_buf fJmpBuf;
+    class AutoPushJmpBuf {
+    public:
+        AutoPushJmpBuf(skjpeg_error_mgr* mgr) : fMgr(mgr) {
+            fMgr->fJmpBufStack.push_back(&fJmpBuf);
+        }
+        ~AutoPushJmpBuf() {
+            SkASSERT(fMgr->fJmpBufStack.back() == &fJmpBuf);
+            fMgr->fJmpBufStack.pop_back();
+        }
+        operator jmp_buf&() { return fJmpBuf; }
+
+    private:
+        skjpeg_error_mgr* const fMgr;
+        jmp_buf fJmpBuf;
+    };
+
+    SkSTArray<4, jmp_buf*> fJmpBufStack;
 };
 
 #endif