8e6c0c14a4
While using libredirect in conjunction with geckodriver, I stumbled on
odd segfaults that happened when running the wrapped statx() call from
libredirect:
0x00007ffff7ddd541 in __strncmp_avx2 () from .../lib/libc.so.6
0x00007ffff7f6fe57 in statx () from .../lib/libredirect.so
0x00005555558d35bd in std::sys::unix::fs::try_statx::h2045d39b0c66d4e8 ()
0x00005555558d2230 in std::sys::unix::fs::stat::ha063998dfb361520 ()
0x0000555555714019 in mozversion::firefox_version::hdc3b57eb04947426 ()
0x00005555556a603c in geckodriver::capabilities::FirefoxCapabilities::version::h58e289917bd3c721 ()
0x00005555556a77f5 in <geckodriver::capabilities::FirefoxCapabilities as webdriver::capabilities::BrowserCapabilities>::validate_custom::h62d23cf9fd63b719 ()
0x000055555562a7c8 in webdriver::capabilities::SpecNewSessionParameters::validate::h60da250d33f0989f ()
0x00005555556d7a13 in <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold::h9427a360a3d0bf8f ()
0x0000555555669d85 in <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter::hd274d536ea29bb33 ()
0x00005555555c05ef in core::iter::adapters::try_process::hdf96a01ec1f9b8bd ()
0x000055555561768d in <webdriver::capabilities::SpecNewSessionParameters as webdriver::capabilities::CapabilitiesMatching>::match_browser::hfbd8c38f6db17e9f ()
0x00005555555ca6ef in <geckodriver::marionette::MarionetteHandler as webdriver::server::WebDriverHandler<geckodriver::command::GeckoExtensionRoute>>::handle_command::h13b98b9cb87a69d6 ()
0x00005555555e859e in webdriver::server::Dispatcher<T,U>::run::h746a8bf2f0bc24fd ()
0x000055555569ff0f in std::sys_common::backtrace::__rust_begin_short_backtrace::h3b920773bd467d2a ()
0x00005555555dbc99 in core::ops::function::FnOnce::call_once{{vtable.shim}}::h81ba7228877515f7 ()
0x00005555558d31a3 in std::sys::unix:🧵:Thread:🆕:thread_start::h4514580219a899c5 ()
0x00007ffff7d0ce24 in start_thread () from .../lib/libc.so.6
0x00007ffff7d8e9b0 in clone3 () from .../lib/libc.so.6
The reason why I found this odd was because it happens in the following
piece of code (shortened a bit):
1 static const char * rewrite(const char * path, char * buf)
2 {
3 if (path == NULL) return path;
4 for (int n = 0; n < nrRedirects; ++n) {
5 int len = strlen(from[n]);
6 if (strncmp(path, from[n], len) != 0) continue;
7 if (snprintf(buf, PATH_MAX, "%s%s", to[n], path + len) >= PATH_MAX)
8 abort();
9 return buf;
10 }
11 return path;
12 }
When inspecting the assembly, I found that the check for the null
pointer in line 3 was completely missing and the code was directly
entering the loop and then eventually segfault when running strncmp()
with a null pointer as its first argument.
I confirmed that indeed that check was missing by compiling libredirect
with "-O0" and comparing the generated assembly with the optimized one.
The one compiled with "-O0" had that check while the optimized one did
not and indeed when running geckodriver with the unoptimized version it
worked fine.
Digging in the Git history, I found
|
||
|---|---|---|
| .github | ||
| doc | ||
| lib | ||
| maintainers | ||
| nixos | ||
| pkgs | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .version | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| default.nix | ||
| flake.nix | ||
| README.md | ||
Nixpkgs is a collection of over 80,000 software packages that can be installed with the Nix package manager. It also implements NixOS, a purely-functional Linux distribution.
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