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author | Corinna Vinschen <corinna@vinschen.de> | 2022-12-01 21:33:14 +0100 |
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committer | Corinna Vinschen <corinna@vinschen.de> | 2022-12-01 22:34:53 +0100 |
commit | 30add3e6b3e3211b3e2d4a093f45bee5c6e24b8b (patch) | |
tree | 6395f10d90550788a94fe37abb53c12f830dda53 /winsup/cygwin/dcrt0.cc | |
parent | e358f8d12f1537a7d0509984207a700205b2c20f (diff) | |
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Cygwin: exec: don't access cygheap before it's initialized
This is a long-standing thinko.
When you exec a process, dll_crt0_0 in the child process calls
child_info_spawn::handle_spawn(). handle_spawn() initialises the
cygheap.
Now consider calling strace. Strace is a non-Cygwin process dynamically
loading cygwin1.dll via LoadLibrary. This in turn initializes the DLL:
- dll_crt0_0 finds that the process it attaches to has been exec'd, so
child_info_spawn::handle_spawn() is called.
- If the DLL is being dynamically loaded, handle_spawn() calls
child_info_spawn::get_parent_handle(). This in turn tries to set
the moreinfo->myself_pinfo value inside the cygheap to NULL.
- However, at this time, the cygheap has not yet been initialized. This
only occurs in the cygheap_fixup_in_child() call after get_parent_handle()
returns.
--> SEGV
This thinko never had a negative side effect, because the cygheap was
pre-allocated at DLL load time until commit 2f9b8ff00cce ("Cygwin:
decouple cygheap from Cygwin DLL"). With 2f9b8ff00cce, the cygheap
actually doesn't exist until after the call to cygheap_fixup_in_child().
Fix this problem by moving the assignment after the call to
cygheap_fixup_in_child().
Fixes: 3de7be4c1deb ("* DevNotes: Add entry cgf-000007. [...]")
Fixes: 2f9b8ff00cce ("Cygwin: decouple cygheap from Cygwin DLL")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Diffstat (limited to 'winsup/cygwin/dcrt0.cc')
-rw-r--r-- | winsup/cygwin/dcrt0.cc | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc index e5f19f1..5c5a280 100644 --- a/winsup/cygwin/dcrt0.cc +++ b/winsup/cygwin/dcrt0.cc @@ -620,7 +620,6 @@ bool child_info_spawn::get_parent_handle () { parent = OpenProcess (PROCESS_VM_READ, FALSE, parent_winpid); - moreinfo->myself_pinfo = NULL; return !!parent; } @@ -632,6 +631,8 @@ child_info_spawn::handle_spawn () if (!dynamically_loaded || get_parent_handle ()) { cygheap_fixup_in_child (true); + if (dynamically_loaded) + moreinfo->myself_pinfo = NULL; memory_init (); } |