Make stack depth check work with asan's use-after-return
Make stack depth check work with asan's use-after-return
От:
Andres Freund <andres@anarazel.de>
Дата:
Hi, When running asan without further options against the backend, random tests fail because the stack-depth check fails. One can work around that by putting detect_stack_use_after_return=0 into ASAN_OPTIONS (at least with gcc, clang still uses a lot of stack, but i think that's a separate issue). The reason for that breakage is that with the stack-use-after-return logic, stack variables are moved to heap allocations, to allow to detect references to the memory at a later time. That breaks 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. I think we should backpatch this. I'd be worried about using __builtin_frame_address(), but we already do, for the base address of the stack. Greetings, Andres Freund
Re: Make stack depth check work with asan's use-after-return
От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Andres Freund writes: > The reason for that breakage is that with the stack-use-after-return logic, > stack variables are moved to heap allocations, to allow to detect references > to the memory at a later time. That breaks 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. > I think we should backpatch this. I'd be worried about using > __builtin_frame_address(), but we already do, for the base address of the > stack. +1. It was a little weird that we adopted __builtin_frame_address() to measure the location of the stack bottom but not the stack top. So I think this is good cleanup even if ASAN weren't forcing it. I might write the comments a bit differently, in particular I suggest changing - * Compute distance from reference point to my local variables + * Compute distance from reference point to my stack frame regards, tom lane
Re: Make stack depth check work with asan's use-after-return
От:
Andres Freund <andres@anarazel.de>
Дата:
Hi, On 2026-05-27 09:54:51 -0400, Tom Lane wrote: > Andres Freund writes: > > The reason for that breakage is that with the stack-use-after-return logic, > > stack variables are moved to heap allocations, to allow to detect references > > to the memory at a later time. That breaks 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. > > I think we should backpatch this. I'd be worried about using > > __builtin_frame_address(), but we already do, for the base address of the > > stack. > > +1. It was a little weird that we adopted __builtin_frame_address() > to measure the location of the stack bottom but not the stack top. > So I think this is good cleanup even if ASAN weren't forcing it. Agreed. > I might write the comments a bit differently, in particular I suggest > changing > > - * Compute distance from reference point to my local variables > + * Compute distance from reference point to my stack frame Changed that, did some other minor comment polishing, and pushed the changes. One annoying thing when backpatching is that in the older branches we still used long. I ended up leaving that aspect as it was, but it didn't feel good :) Thanks for reviewing. - Andres
