diff mbox series

[02/10] linux-user: Fix parse_elf_properties GNU0_MAGIC check

Message ID 20241005233343.503426-3-richard.henderson@linaro.org
State New
Headers show
Series linux-user pre-PR | expand

Commit Message

Richard Henderson Oct. 5, 2024, 11:33 p.m. UTC 
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>
---
 linux-user/elfload.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Comments

Philippe Mathieu-Daudé Oct. 7, 2024, 7:50 p.m. UTC | #1 
On 5/10/24 20:33, Richard Henderson wrote:
> 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>
> ---
>   linux-user/elfload.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
diff mbox series

Patch

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 0678c9d506..52c88a68a9 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -3121,11 +3121,11 @@  static bool parse_elf_properties(const ImageSource *src,
     }
 
     /*
-     * 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 @@  static bool parse_elf_properties(const ImageSource *src,
      * 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;