Perl: propagate errors.

When an error happens, the ctx->error bit is now set, and croak()
is called to terminate further processing.  The ctx->error bit is
checked in ngx_http_perl_call_handler() to cancel further processing,
and is also checked in various output functions - to make sure these won't
be called if croak() was handled by an eval{} in perl code.

In particular, this ensures that output chain won't be called after
errors, as filters might not expect this to happen.  This fixes some
segmentation faults under low memory conditions.  Also this stops
request processing after filter finalization or request body reading
errors.

For cases where an HTTP error status can be additionally returned (for
example, 416 (Requested Range Not Satisfiable) from the range filter),
the ctx->status field is also added.

3 files changed, 90 insertions, 7 deletions

diff --git a/src/http/modules/perl/nginx.xs b/src/http/modules/perl/nginx.xs
index 2e9808f2b..8e17f6d57 100644
--- a/src/http/modules/perl/nginx.xs
+++ b/src/http/modules/perl/nginx.xs
@@ -125,9 +125,14 @@ send_http_header(r, ...)
     ngx_http_request_t   *r;
     ngx_http_perl_ctx_t  *ctx;
     SV                   *sv;
+    ngx_int_t             rc;
 
     ngx_http_perl_set_request(r, ctx);
 
+    if (ctx->error) {
+        croak("send_http_header(): called after error");
+    }
+
     if (r->headers_out.status == 0) {
         r->headers_out.status = NGX_HTTP_OK;
     }
@@ -151,7 +156,13 @@ send_http_header(r, ...)
 
     r->disable_not_modified = 1;
 
-    (void) ngx_http_send_header(r);
+    rc = ngx_http_send_header(r);
+
+    if (rc == NGX_ERROR || rc > NGX_OK) {
+        ctx->error = 1;
+        ctx->status = rc;
+        croak("ngx_http_send_header() failed");
+    }
 
 
 void
@@ -381,6 +392,7 @@ has_request_body(r, next)
     dXSTARG;
     ngx_http_request_t   *r;
     ngx_http_perl_ctx_t  *ctx;
+    ngx_int_t             rc;
 
     ngx_http_perl_set_request(r, ctx);
 
@@ -398,7 +410,14 @@ has_request_body(r, next)
         r->request_body_file_log_level = 0;
     }
 
-    ngx_http_read_client_request_body(r, ngx_http_perl_handle_request);
+    rc = ngx_http_read_client_request_body(r, ngx_http_perl_handle_request);
+
+    if (rc >= NGX_HTTP_SPECIAL_RESPONSE) {
+        ctx->error = 1;
+        ctx->status = rc;
+        ctx->next = NULL;
+        croak("ngx_http_read_client_request_body() failed");
+    }
 
     sv_upgrade(TARG, SVt_IV);
     sv_setiv(TARG, 1);
@@ -494,10 +513,17 @@ discard_request_body(r)
 
     ngx_http_request_t   *r;
     ngx_http_perl_ctx_t  *ctx;
+    ngx_int_t             rc;
 
     ngx_http_perl_set_request(r, ctx);
 
-    ngx_http_discard_request_body(r);
+    rc = ngx_http_discard_request_body(r);
+
+    if (rc != NGX_OK) {
+        ctx->error = 1;
+        ctx->status = rc;
+        croak("ngx_http_discard_request_body() failed");
+    }
 
 
 void
@@ -512,6 +538,10 @@ header_out(r, key, value)
 
     ngx_http_perl_set_request(r, ctx);
 
+    if (ctx->error) {
+        croak("header_out(): called after error");
+    }
+
     key = ST(1);
     value = ST(2);
 
@@ -588,10 +618,15 @@ print(r, ...)
     u_char               *p;
     size_t                size;
     STRLEN                len;
+    ngx_int_t             rc;
     ngx_buf_t            *b;
 
     ngx_http_perl_set_request(r, ctx);
 
+    if (ctx->error) {
+        croak("print(): called after error");
+    }
+
     if (items == 2) {
 
         /*
@@ -671,7 +706,12 @@ print(r, ...)
 
     out:
 
-    (void) ngx_http_perl_output(r, ctx, b);
+    rc = ngx_http_perl_output(r, ctx, b);
+
+    if (rc == NGX_ERROR) {
+        ctx->error = 1;
+        croak("ngx_http_perl_output() failed");
+    }
 
 
 void
@@ -683,6 +723,7 @@ sendfile(r, filename, offset = -1, bytes = 0)
     char                      *filename;
     off_t                      offset;
     size_t                     bytes;
+    ngx_int_t                  rc;
     ngx_str_t                  path;
     ngx_buf_t                 *b;
     ngx_open_file_info_t       of;
@@ -690,6 +731,10 @@ sendfile(r, filename, offset = -1, bytes = 0)
 
     ngx_http_perl_set_request(r, ctx);
 
+    if (ctx->error) {
+        croak("sendfile(): called after error");
+    }
+
     filename = SvPV_nolen(ST(1));
 
     if (filename == NULL) {
@@ -762,7 +807,12 @@ sendfile(r, filename, offset = -1, bytes = 0)
     b->file->log = r->connection->log;
     b->file->directio = of.is_directio;
 
-    (void) ngx_http_perl_output(r, ctx, b);
+    rc = ngx_http_perl_output(r, ctx, b);
+
+    if (rc == NGX_ERROR) {
+        ctx->error = 1;
+        croak("ngx_http_perl_output() failed");
+    }
 
 
 void
@@ -771,10 +821,15 @@ flush(r)
 
     ngx_http_request_t   *r;
     ngx_http_perl_ctx_t  *ctx;
+    ngx_int_t             rc;
     ngx_buf_t            *b;
 
     ngx_http_perl_set_request(r, ctx);
 
+    if (ctx->error) {
+        croak("flush(): called after error");
+    }
+
     b = ngx_calloc_buf(r->pool);
     if (b == NULL) {
         XSRETURN_EMPTY;
@@ -784,7 +839,12 @@ flush(r)
 
     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "$r->flush");
 
-    (void) ngx_http_perl_output(r, ctx, b);
+    rc = ngx_http_perl_output(r, ctx, b);
+
+    if (rc == NGX_ERROR) {
+        ctx->error = 1;
+        croak("ngx_http_perl_output() failed");
+    }
 
     XSRETURN_EMPTY;
 
diff --git a/src/http/modules/perl/ngx_http_perl_module.c b/src/http/modules/perl/ngx_http_perl_module.c
index c2ef47048..ac6a7a2a3 100644
--- a/src/http/modules/perl/ngx_http_perl_module.c
+++ b/src/http/modules/perl/ngx_http_perl_module.c
@@ -246,6 +246,11 @@ ngx_http_perl_handle_request(ngx_http_request_t *r)
     ctx->filename.data = NULL;
     ctx->redirect_uri.len = 0;
 
+    if (rc == NGX_ERROR) {
+        ngx_http_finalize_request(r, rc);
+        return;
+    }
+
     if (ctx->done || ctx->next) {
         ngx_http_finalize_request(r, NGX_DONE);
         return;
@@ -690,6 +695,9 @@ ngx_http_perl_call_handler(pTHX_ ngx_http_request_t *r,
 
     status = 0;
 
+    ctx->error = 0;
+    ctx->status = NGX_OK;
+
     ENTER;
     SAVETMPS;
 
@@ -739,6 +747,18 @@ ngx_http_perl_call_handler(pTHX_ ngx_http_request_t *r,
     FREETMPS;
     LEAVE;
 
+    if (ctx->error) {
+
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                       "call_sv: error, %d", ctx->status);
+
+        if (ctx->status != NGX_OK) {
+            return ctx->status;
+        }
+
+        return NGX_ERROR;
+    }
+
     /* check $@ */
 
     if (SvTRUE(ERRSV)) {
diff --git a/src/http/modules/perl/ngx_http_perl_module.h b/src/http/modules/perl/ngx_http_perl_module.h
index 4f1eaa3a2..5c967dfb3 100644
--- a/src/http/modules/perl/ngx_http_perl_module.h
+++ b/src/http/modules/perl/ngx_http_perl_module.h
@@ -29,7 +29,10 @@ typedef struct {
 
     SV                       *next;
 
-    ngx_uint_t                done;       /* unsigned  done:1; */
+    ngx_int_t                 status;
+
+    unsigned                  done:1;
+    unsigned                  error:1;
 
     ngx_array_t              *variables;  /* array of ngx_http_perl_var_t */