[Tarantool-patches] [PATCH luajit v2] Fix frame traversal for __gc handler frames.
Igor Munkin
imun at tarantool.org
Tue Nov 23 15:57:38 MSK 2021
Sergey,
Thanks for the fixes! LGTM, with a tiny nit.
On 19.11.21, Sergey Kaplun wrote:
> From: Mike Pall <mike>
>
> Reported by Changochen.
>
> (cherry picked from 53f82e6e2e858a0a62fd1a2ff47e9866693382e6)
>
> A cframe unwinding is missed for a C protected frame during a search for
> an error function to handle a runtime error. It leads to undefined
> behaviour or crash, when raising a runtime error on stack with the CP
> frame before an error function handler (for example, an error in __gc
> handler).
>
> This patch adds missing unwinding for CP frame.
>
> Sergey Kaplun:
> * added the description and the test for the problem
> ---
>
> LuaJIT issue: https://github.com/LuaJIT/LuaJIT/issues/601
> Branch: https://github.com/tarantool/luajit/tree/skaplun/gh-noticket-fix-gc-finderrfunc
> Tarantool branch: https://github.com/tarantool/tarantool/tree/skaplun/gh-noticket-fix-gc-finderrfunc
>
> Changes in v2:
> * Create CP and C stack manually in LuaC
>
> src/lj_err.c | 1 +
> test/tarantool-tests/CMakeLists.txt | 1 +
> .../lj-601-fix-gc-finderrfunc.test.lua | 35 ++++++++++++
> .../lj-601-fix-gc-finderrfunc/CMakeLists.txt | 1 +
> .../lj-601-fix-gc-finderrfunc/mixcframe.c | 55 +++++++++++++++++++
> 5 files changed, 93 insertions(+)
> create mode 100644 test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua
> create mode 100644 test/tarantool-tests/lj-601-fix-gc-finderrfunc/CMakeLists.txt
> create mode 100644 test/tarantool-tests/lj-601-fix-gc-finderrfunc/mixcframe.c
>
<snipped>
> diff --git a/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua b/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua
> new file mode 100644
> index 00000000..d4c44489
> --- /dev/null
> +++ b/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua
> @@ -0,0 +1,35 @@
<snipped>
> +local a = newproxy(true)
> +getmetatable(a).__gc = function()
> + -- Function to raise error via `lj_err_run()` inside __gc.
> + error('raise error in __gc')
> +end
> +-- luacheck: no unused
> +a = nil
> +
> +-- We need to get the following Lua stack format when raise an
> +-- error:
> +-- + L->stack
> +-- | ...
> +-- | CP -- any C protected frame.
> +-- | ...[L/LP/V]...
> +-- | C -- any C frame.
> +-- | ...[L/LP/V]...
> +-- | CP (with inherited errfunc) -- __gc frame.
> +-- V
> +-- Enter in the C to call CP func. Call `lua_gc()` inside.
Minor: I'd adjust this comment the following way:
| -- Enter in the C land to call a function in a protected C frame
| -- (CP). Spoil host stack (and ergo cframe area) and later call
| -- Lua C function, triggering full GC cycle in a non-protected
| -- frame. As a result, error is raised in __gc metamethod above.
Fixed, squashed, force-pushed to the branch. Diff is below:
================================================================================
diff --git a/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua b/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua
index d4c44489..2122c7a0 100644
--- a/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua
+++ b/test/tarantool-tests/lj-601-fix-gc-finderrfunc.test.lua
@@ -29,7 +29,10 @@ a = nil
-- | ...[L/LP/V]...
-- | CP (with inherited errfunc) -- __gc frame.
-- V
--- Enter in the C to call CP func. Call `lua_gc()` inside.
+-- Enter in the C land to call a function in a protected C frame
+-- (CP). Spoil host stack (and ergo cframe area) and later call
+-- Lua C function, triggering full GC cycle in a non-protected
+-- frame. As a result, error is raised in __gc metamethod above.
test:ok(mixcframe.test_handle_err(), 'error in __gc is successfully handled')
os.exit(test:check() and 0 or 1)
================================================================================
> +test:ok(mixcframe.test_handle_err(), 'error in __gc is successfully handled')
> +
> +os.exit(test:check() and 0 or 1)
<snipped>
> --
> 2.31.0
>
--
Best regards,
IM
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