libsanitizer: Hwasan reporting check for dladdr failing

[Matthew Malcomson via Gcc-patches]

Hello there,

This is the compiler-rt patch I'd like to cherry-pick so that the hwasan tests
pass.

It is in LLVM as commit 83ac18205ec69a00ac2be3b603bc3a61293fbe89.

Ok for trunk?

Also is the libhwasan library merge from the below email OK for trunk?
https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558999.html
(Note I would also add a line to README.gcc mentioning compiler-rt/lib/hwasan
on top of the changes in that patch).

I would guess so, but wasn't certain the OK had ever been said anywhere.

Regards,
Matthew

-------------------------


In `GetGlobalSizeFromDescriptor` we use `dladdr` to get info on the the
current address.  `dladdr` returns 0 if it failed.
During testing on Linux this returned 0 to indicate failure, and
populated the `info` structure with a NULL pointer which was
dereferenced later.

This patch checks for `dladdr` returning 0, and in that case returns 0
from `GetGlobalSizeFromDescriptor` to indicate failure of identifying
the address.

This occurs when `GetModuleNameAndOffsetForPC` succeeds for some address
not in a dynamically loaded library.  One example is when the found
"module" is '[stack]' having come from parsing /proc/self/maps.

Cherry-pick from 83ac18205ec69a00ac2be3b603bc3a61293fbe89.

Differential Revision: https://reviews.llvm.org/D91344


###############     Attachment also inlined for ease of reply    ###############


diff --git a/libsanitizer/hwasan/hwasan_report.cpp 
b/libsanitizer/hwasan/hwasan_report.cpp
index 
0be7deeaee1a0bd523d9e0fe1dc3b1311b3920e2..894a149775f291bae9cad833b1ac54914212f405
 100644
--- a/libsanitizer/hwasan/hwasan_report.cpp
+++ b/libsanitizer/hwasan/hwasan_report.cpp
@@ -254,7 +254,8 @@ static bool TagsEqual(tag_t tag, tag_t *tag_ptr) {
 static uptr GetGlobalSizeFromDescriptor(uptr ptr) {
   // Find the ELF object that this global resides in.
   Dl_info info;
-  dladdr(reinterpret_cast<void *>(ptr), &info);
+  if (dladdr(reinterpret_cast<void *>(ptr), &info) == 0)
+    return 0;
   auto *ehdr = reinterpret_cast<const ElfW(Ehdr) *>(info.dli_fbase);
   auto *phdr_begin = reinterpret_cast<const ElfW(Phdr) *>(
       reinterpret_cast<const u8 *>(ehdr) + ehdr->e_phoff);


diff --git a/libsanitizer/hwasan/hwasan_report.cpp 
b/libsanitizer/hwasan/hwasan_report.cpp
index 
0be7deeaee1a0bd523d9e0fe1dc3b1311b3920e2..894a149775f291bae9cad833b1ac54914212f405
 100644
--- a/libsanitizer/hwasan/hwasan_report.cpp
+++ b/libsanitizer/hwasan/hwasan_report.cpp
@@ -254,7 +254,8 @@ static bool TagsEqual(tag_t tag, tag_t *tag_ptr) {
 static uptr GetGlobalSizeFromDescriptor(uptr ptr) {
   // Find the ELF object that this global resides in.
   Dl_info info;
-  dladdr(reinterpret_cast<void *>(ptr), &info);
+  if (dladdr(reinterpret_cast<void *>(ptr), &info) == 0)
+    return 0;
   auto *ehdr = reinterpret_cast<const ElfW(Ehdr) *>(info.dli_fbase);
   auto *phdr_begin = reinterpret_cast<const ElfW(Phdr) *>(
       reinterpret_cast<const u8 *>(ehdr) + ehdr->e_phoff);