Message ID | trinity-ba957585-31b4-421f-8f1f-650fb1f43158-1613682741374@3c-app-gmx-bap37 |
---|---|
State | New |
Headers | show |
Series | PR fortran/99147 - Sanitizer detects heap-use-after-free in gfc_add_flavor | expand |
Hi Harald, It looks 'obvious' to me too and is certainly OK for master. Thanks Paul On Thu, 18 Feb 2021 at 21:30, Harald Anlauf via Fortran <fortran@gcc.gnu.org> wrote: > Dear all, > > the PR reports an issue detected with an ASAN instrumented compiler, > which can also be verified with valgrind. It appears that the state > of gfc_new_block could be such that it should not be dereferenced. > Reversing the order of condition evaluation helped. > > I failed to find out why this should happen, but then other places > in the code put dereferences of gfc_new_block behind other checks. > Simple things like initializing gfc_new_block with NULL in decl.c > did not help. > > Regtested on x86_64-pc-linux-gnu. No testcase added since the issue > can be found only with an instrumented compiler or valgrind. > > I consider the patch to be obvious and trivial, but post it here > in case somebody wants to dig deeper. > > OK for master? > > Thanks, > Harald > > > PR fortran/99147 - Sanitizer detects heap-use-after-free in gfc_add_flavor > > Reverse order of conditions to avoid invalid read. > > gcc/fortran/ChangeLog: > > * symbol.c (gfc_add_flavor): Reverse order of conditions. > >
diff --git a/gcc/fortran/symbol.c b/gcc/fortran/symbol.c index 3b988d1be22..e982374d9d1 100644 --- a/gcc/fortran/symbol.c +++ b/gcc/fortran/symbol.c @@ -1772,8 +1772,8 @@ gfc_add_flavor (symbol_attribute *attr, sym_flavor f, const char *name, /* Copying a procedure dummy argument for a module procedure in a submodule results in the flavor being copied and would result in an error without this. */ - if (gfc_new_block && gfc_new_block->abr_modproc_decl - && attr->flavor == f && f == FL_PROCEDURE) + if (attr->flavor == f && f == FL_PROCEDURE + && gfc_new_block && gfc_new_block->abr_modproc_decl) return true; if (attr->flavor != FL_UNKNOWN)