commit 2884596f5f385b5712c356310dd4125a089888a8
author Richard Henderson <richard.henderson@linaro.org> Sat Oct 05 09:01:22 2024 -0700
committer Richard Henderson <richard.henderson@linaro.org> Tue Oct 08 06:31:22 2024 -0700
tree 93dadc6e15ee87dbc14b722578eb6d3064a2e8c4
parent a9ee641bd46f5462eeed183ac3c3760bddfc2600

linux-user: Fix parse_elf_properties GNU0_MAGIC check

Comparing a string of 4 bytes only works in little-endian.

Adjust bulk bswap to only apply to the note payload.
Perform swapping of the note header manually; the magic
is defined so that it does not need a runtime swap.

Fixes: 83f990eb5adb ("linux-user/elfload: Parse NT_GNU_PROPERTY_TYPE_0 notes")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2596
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>

linux-user/elfload.c

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 0678c9d..52c88a6 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -3121,11 +3121,11 @@
     }
 
     /*
-     * The contents of a valid PT_GNU_PROPERTY is a sequence
-     * of uint32_t -- swap them all now.
+     * The contents of a valid PT_GNU_PROPERTY is a sequence of uint32_t.
+     * Swap most of them now, beyond the header and namesz.
      */
 #ifdef BSWAP_NEEDED
-    for (int i = 0; i < n / 4; i++) {
+    for (int i = 4; i < n / 4; i++) {
         bswap32s(note.data + i);
     }
 #endif
@@ -3135,15 +3135,15 @@
      * immediately follows nhdr and is thus at the 4th word.  Further, all
      * of the inputs to the kernel's round_up are multiples of 4.
      */
-    if (note.nhdr.n_type != NT_GNU_PROPERTY_TYPE_0 ||
-        note.nhdr.n_namesz != NOTE_NAME_SZ ||
+    if (tswap32(note.nhdr.n_type) != NT_GNU_PROPERTY_TYPE_0 ||
+        tswap32(note.nhdr.n_namesz) != NOTE_NAME_SZ ||
         note.data[3] != GNU0_MAGIC) {
         error_setg(errp, "Invalid note in PT_GNU_PROPERTY");
         return false;
     }
     off = sizeof(note.nhdr) + NOTE_NAME_SZ;
 
-    datasz = note.nhdr.n_descsz + off;
+    datasz = tswap32(note.nhdr.n_descsz) + off;
     if (datasz > n) {
         error_setg(errp, "Invalid note size in PT_GNU_PROPERTY");
         return false;