From f6be0d483b29e669164565ee5f36f464991b3357 Mon Sep 17 00:00:00 2001
From: Giovanni Mascellani <address@hidden>
Date: Sun, 13 Jan 2019 10:29:25 +0100
Subject: [PATCH] Fix read() usage in tccelf.c.

read() is allowed to short-read, and return less bytes then requested.
The caller must restart read() when this happens (and they want more
bytes).

This patch is still buggy, because errors are not always checked.
Still, less buggy than before.
---
 tccelf.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/tccelf.c b/tccelf.c
index 9f242b8..0a5ba71 100644
--- a/tccelf.c
+++ b/tccelf.c
@@ -2246,13 +2246,25 @@ LIBTCCAPI int tcc_output_file(TCCState *s, const char *filename)
     return ret;
 }
 
+ssize_t full_read(int fd, void *buf, size_t count) {
+    char *cbuf = buf;
+    size_t rnum = 0;
+    while (1) {
+        ssize_t num = read(fd, cbuf, count-rnum);
+        if (num < 0) return num;
+        if (num == 0) return rnum;
+        rnum += num;
+        cbuf += num;
+    }
+}
+
 static void *load_data(int fd, unsigned long file_offset, unsigned long size)
 {
     void *data;
 
     data = tcc_malloc(size);
     lseek(fd, file_offset, SEEK_SET);
-    read(fd, data, size);
+    full_read(fd, data, size);
     return data;
 }
 
@@ -2265,7 +2277,7 @@ typedef struct SectionMergeInfo {
 
 ST_FUNC int tcc_object_type(int fd, ElfW(Ehdr) *h)
 {
-    int size = read(fd, h, sizeof *h);
+    int size = full_read(fd, h, sizeof *h);
     if (size == sizeof *h && 0 == memcmp(h, ELFMAG, 4)) {
         if (h->e_type == ET_REL)
             return AFF_BINTYPE_REL;
@@ -2434,7 +2446,7 @@ ST_FUNC int tcc_load_object_file(TCCState *s1,
             unsigned char *ptr;
             lseek(fd, file_offset + sh->sh_offset, SEEK_SET);
             ptr = section_ptr_add(s, size);
-            read(fd, ptr, size);
+            full_read(fd, ptr, size);
         } else {
             s->data_offset += size;
         }
@@ -2606,7 +2618,7 @@ static int tcc_load_alacarte(TCCState *s1, int fd, int size, int entrysize)
     ElfW(Sym) *sym;
 
     data = tcc_malloc(size);
-    if (read(fd, data, size) != size)
+    if (full_read(fd, data, size) != size)
         goto fail;
     nsyms = entrysize == 4 ? get_be32(data) : get_be64(data);
     ar_index = data + entrysize;
@@ -2650,10 +2662,10 @@ ST_FUNC int tcc_load_archive(TCCState *s1, int fd, int alacarte)
     unsigned long file_offset;
 
     /* skip magic which was already checked */
-    read(fd, magic, sizeof(magic));
+    full_read(fd, magic, sizeof(magic));
 
     for(;;) {
-        len = read(fd, &hdr, sizeof(hdr));
+        len = full_read(fd, &hdr, sizeof(hdr));
         if (len == 0)
             break;
         if (len != sizeof(hdr)) {
@@ -2706,7 +2718,7 @@ ST_FUNC int tcc_load_dll(TCCState *s1, int fd, const char *filename, int level)
     const char *name, *soname;
     DLLReference *dllref;
 
-    read(fd, &ehdr, sizeof(ehdr));
+    full_read(fd, &ehdr, sizeof(ehdr));
 
     /* test CPU specific stuff */
     if (ehdr.e_ident[5] != ELFDATA2LSB ||
-- 
2.20.1