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Make stack depth check work with asan's use-after-return

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With address sanitizer's stack-use-after-return check, stack variables are
moved to heap allocations, to allow to detect references to the memory at a
later time. That broke our stack-depth check, which is why we had to disable
detect_stack_use_after_return in CI. Luckily __builtin_frame_address() works
correctly, even under asan, so use that.

We started using __builtin_frame_address() with de447bb8e6, however as of
that commit we just used it for the stack base address, not for the value to
compare to the base address.  Now we use it for both.

When building without __builtin_frame_address() support, we continue to use
stack variables for the stack depth determination.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/2kk4z4odvuyrg7qlwjd7ft4eron4cle4btb33v4qatgsdkayir@gj6e62rgsel4
Backpatch-through: 14
This commit is contained in:
Andres Freund 2026-05-28 11:34:13 -04:00
parent cdb9b2830d
commit 970ac13791
2 changed files with 20 additions and 4 deletions
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2
.cirrus.tasks.yml
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@ -271,7 +271,7 @@ task:
# print_stacktraces=1,verbosity=2, duh
# detect_leaks=0: too many uninteresting leak errors in short-lived binaries
UBSAN_OPTIONS: print_stacktrace=1:disable_coredump=0:abort_on_error=1:verbosity=2
ASAN_OPTIONS: print_stacktrace=1:disable_coredump=0:abort_on_error=1:detect_leaks=0:detect_stack_use_after_return=0
ASAN_OPTIONS: print_stacktrace=1:disable_coredump=0:abort_on_error=1:detect_leaks=0
# SANITIZER_FLAGS is set in the tasks below
CFLAGS: -Og -ggdb -fno-sanitize-recover=all $SANITIZER_FLAGS

22
src/backend/tcop/postgres.c
View file

@ -3495,7 +3495,8 @@ set_stack_base(void)
/*
* Set up reference point for stack depth checking. On recent gcc we use
* __builtin_frame_address() to avoid a warning about storing a local
* variable's address in a long-lived variable.
* variable's address in a long-lived variable. This is also important
* with address sanitizer, see comment in stack_is_too_deep().
*/
#ifdef HAVE__BUILTIN_FRAME_ADDRESS
stack_base_ptr = __builtin_frame_address(0);
@ -3549,13 +3550,28 @@ check_stack_depth(void)
bool
stack_is_too_deep(void)
{
#ifndef HAVE__BUILTIN_FRAME_ADDRESS
char stack_top_loc;
#endif
long stack_depth;
char *stack_address;
/*
* Compute distance from reference point to my local variables
* With address sanitizer's stack-use-after-return check, stack variables
* are moved to heap allocations, to allow to detect references to the
* memory at a later time. That would break our stack-depth check. Luckily
* __builtin_frame_address() works correctly, even under asan.
*/
stack_depth = (long) (stack_base_ptr - &stack_top_loc);
#ifndef HAVE__BUILTIN_FRAME_ADDRESS
stack_address = &stack_top_loc;
#else
stack_address = (char *) __builtin_frame_address(0);
#endif
/*
* Compute distance from reference point to my stack frame.
*/
stack_depth = (long) (stack_base_ptr - stack_address);
/*
* Take abs value, since stacks grow up on some machines, down on others