RUST_BACKTRACE on macOS can trigger crashes #71397
Labels
A-runtime
Area: std's runtime and "pre-main" init for handling backtraces, unwinds, stack overflows
C-bug
Category: This is a bug.
O-macos
Operating system: macOS
regression-from-stable-to-nightly
Performance or correctness regression from stable to nightly.
T-libs-api
Relevant to the library API team, which will review and decide on the PR/issue.
Comments
jdm
added
regression-from-stable-to-nightly
|
I found this as part of Servo's unit test suite, which now has intermittent segfaults in #[should_panic] tests on CI with nightlies since 3/26. I've also reproduced this by adding a panic!() in https://github.com/Kethku/neovide/blob/56cc29d47ccbff7cf823a738b3f7f4a31e8af26d/src/window.rs#L150, but I haven't yet been able to create a standalone unit test that demonstrates the issue. |
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It looks like the code that is crashing was introduced as part of rust-lang/libbacktrace@4e548e7, which was brought in as part of the submodule update in rust-lang/backtrace-rs@703aeee. |
jonas-schievink
added
A-runtime
|
Here's a standalone testcase that reproduces the problem for me: [package]
name = "panic_test"
version = "0.1.0"
authors = ["Josh Matthews <josh@joshmatthews.net>"]
edition = "2018"
[dependencies]
core-graphics = "*"main.rs: fn main() {
let a = core_graphics::color::CGColor::rgb(0., 0., 0., 0.);
panic!()
} |
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I have a suspicion that my testcase only works because of #56068 right now. |
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Can you open an issue on backtrace-rs? |
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Filed rust-lang/backtrace-rs#312. |
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rust-lang/backtrace-rs#312 (comment) reports that pulling in an updated backtrace-rs to rustc should fix this. |
Thomasdezeeuw
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Apr 28, 2020
Caused by a problem in libbacktrace first reported to rust repo in rust-lang/rust#71397, than to backtrac-rs in rust-lang/backtrace-rs#312, fixed in backtrace-rs here: rust-lang/backtrace-rs@b53c52b. Update of backtrace-rs for rustc is here: rust-lang/rust#71577, no yet merged.
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I think I am getting this on a stable rustc 1.44.0 (49cae55 2020-06-01) on macOS 10.15.5. when I tried to launch the same code under lldd it panicked properly (I tried a dozen of times). Then, another test run has led to a stall. /usr/bin/sample for the process showed this: which led me to this issue. |
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@pepyakin I think the fix for this isn't in 1.44, it should be in 1.45, though. Can you test to see if the issue is fixed on beta? |
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I tried to rebuild and re-run the test and I couldn't reproduce this issue again with beta! |
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netbsd-srcmastr
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Jul 7, 2020
Pkgsrc changes: * None. Upstream changes: Version 1.44.1 (2020-06-18) =========================== * [rustfmt accepts rustfmt_skip in cfg_attr again.][73078] * [Don't hash executable filenames on apple platforms, fixing backtraces.] [cargo/8329] * [Fix crashes when finding backtrace on macOS.][71397] * [Clippy applies lint levels into different files.][clippy/5356] [71397]: rust-lang/rust#71397 [73078]: rust-lang/rust#73078 [cargo/8329]: rust-lang/cargo#8329 [clippy/5356]: rust-lang/rust-clippy#5356
alexcrichton
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Jul 17, 2020
This commit is a proof-of-concept for switching the standard library's backtrace symbolication mechanism on most platforms from libbacktrace to gimli. The standard library's support for `RUST_BACKTRACE=1` requires in-process parsing of object files and DWARF debug information to interpret it and print the filename/line number of stack frames as part of a backtrace. Historically this support in the standard library has come from a library called "libbacktrace". The libbacktrace library seems to have been extracted from gcc at some point and is written in C. We've had a lot of issues with libbacktrace over time, unfortunately, though. The library does not appear to be actively maintained since we've had patches sit for months-to-years without comments. We have discovered a good number of soundness issues with the library itself, both when parsing valid DWARF as well as invalid DWARF. This is enough of an issue that the libs team has previously decided that we cannot feed untrusted inputs to libbacktrace. This also doesn't take into account the portability of libbacktrace which has been difficult to manage and maintain over time. While possible there are lots of exceptions and it's the main C dependency of the standard library right now. For years it's been the desire to switch over to a Rust-based solution for symbolicating backtraces. It's been assumed that we'll be using the Gimli family of crates for this purpose, which are targeted at safely and efficiently parsing DWARF debug information. I've been working recently to shore up the Gimli support in the `backtrace` crate. As of a few weeks ago the `backtrace` crate, by default, uses Gimli when loaded from crates.io. This transition has gone well enough that I figured it was time to start talking seriously about this change to the standard library. This commit is a preview of what's probably the best way to integrate the `backtrace` crate into the standard library with the Gimli feature turned on. While today it's used as a crates.io dependency, this commit switches the `backtrace` crate to a submodule of this repository which will need to be updated manually. This is not done lightly, but is thought to be the best solution. The primary reason for this is that the `backtrace` crate needs to do some pretty nontrivial filesystem interactions to locate debug information. Working without `std::fs` is not an option, and while it might be possible to do some sort of trait-based solution when prototyped it was found to be too unergonomic. Using a submodule allows the `backtrace` crate to build as a submodule of the `std` crate itself, enabling it to use `std::fs` and such. Otherwise this adds new dependencies to the standard library. This step requires extra attention because this means that these crates are now going to be included with all Rust programs by default. It's important to note, however, that we're already shipping libbacktrace with all Rust programs by default and it has a bunch of C code implementing all of this internally anyway, so we're basically already switching already-shipping functionality to Rust from C. * `object` - this crate is used to parse object file headers and contents. Very low-level support is used from this crate and almost all of it is disabled. Largely we're just using struct definitions as well as convenience methods internally to read bytes and such. * `addr2line` - this is the main meat of the implementation for symbolication. This crate depends on `gimli` for DWARF parsing and then provides interfaces needed by the `backtrace` crate to turn an address into a filename / line number. This crate is actually pretty small (fits in a single file almost!) and mirrors most of what `dwarf.c` does for libbacktrace. * `miniz_oxide` - the libbacktrace crate transparently handles compressed debug information which is compressed with zlib. This crate is used to decompress compressed debug sections. * `gimli` - not actually used directly, but a dependency of `addr2line`. * `adler32`- not used directly either, but a dependency of `miniz_oxide`. The goal of this change is to improve the safety of backtrace symbolication in the standard library, especially in the face of possibly malformed DWARF debug information. Even to this day we're still seeing segfaults in libbacktrace which could possibly become security vulnerabilities. This change should almost entirely eliminate this possibility whilc also paving the way forward to adding more features like split debug information. Some references for those interested are: * Original addition of libbacktrace - rust-lang#12602 * OOM with libbacktrace - rust-lang#24231 * Backtrace failure due to use of uninitialized value - rust-lang#28447 * Possibility to feed untrusted data to libbacktrace - rust-lang#21889 * Soundness fix for libbacktrace - rust-lang#33729 * Crash in libbacktrace - rust-lang#39468 * Support for macOS, never merged - ianlancetaylor/libbacktrace#2 * Performance issues with libbacktrace - rust-lang#29293, rust-lang#37477 * Update procedure is quite complicated due to how many patches we need to carry - rust-lang#50955 * Libbacktrace doesn't work on MinGW with dynamic libs - rust-lang#71060 * Segfault in libbacktrace on macOS - rust-lang#71397 Switching to Rust will not make us immune to all of these issues. The crashes are expected to go away, but correctness and performance may still have bugs arise. The gimli and `backtrace` crates, however, are actively maintained unlike libbacktrace, so this should enable us to at least efficiently apply fixes as situations come up.
bors
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Jul 18, 2020
…Simulacrum std: Switch from libbacktrace to gimli This commit is a proof-of-concept for switching the standard library's backtrace symbolication mechanism on most platforms from libbacktrace to gimli. The standard library's support for `RUST_BACKTRACE=1` requires in-process parsing of object files and DWARF debug information to interpret it and print the filename/line number of stack frames as part of a backtrace. Historically this support in the standard library has come from a library called "libbacktrace". The libbacktrace library seems to have been extracted from gcc at some point and is written in C. We've had a lot of issues with libbacktrace over time, unfortunately, though. The library does not appear to be actively maintained since we've had patches sit for months-to-years without comments. We have discovered a good number of soundness issues with the library itself, both when parsing valid DWARF as well as invalid DWARF. This is enough of an issue that the libs team has previously decided that we cannot feed untrusted inputs to libbacktrace. This also doesn't take into account the portability of libbacktrace which has been difficult to manage and maintain over time. While possible there are lots of exceptions and it's the main C dependency of the standard library right now. For years it's been the desire to switch over to a Rust-based solution for symbolicating backtraces. It's been assumed that we'll be using the Gimli family of crates for this purpose, which are targeted at safely and efficiently parsing DWARF debug information. I've been working recently to shore up the Gimli support in the `backtrace` crate. As of a few weeks ago the `backtrace` crate, by default, uses Gimli when loaded from crates.io. This transition has gone well enough that I figured it was time to start talking seriously about this change to the standard library. This commit is a preview of what's probably the best way to integrate the `backtrace` crate into the standard library with the Gimli feature turned on. While today it's used as a crates.io dependency, this commit switches the `backtrace` crate to a submodule of this repository which will need to be updated manually. This is not done lightly, but is thought to be the best solution. The primary reason for this is that the `backtrace` crate needs to do some pretty nontrivial filesystem interactions to locate debug information. Working without `std::fs` is not an option, and while it might be possible to do some sort of trait-based solution when prototyped it was found to be too unergonomic. Using a submodule allows the `backtrace` crate to build as a submodule of the `std` crate itself, enabling it to use `std::fs` and such. Otherwise this adds new dependencies to the standard library. This step requires extra attention because this means that these crates are now going to be included with all Rust programs by default. It's important to note, however, that we're already shipping libbacktrace with all Rust programs by default and it has a bunch of C code implementing all of this internally anyway, so we're basically already switching already-shipping functionality to Rust from C. * `object` - this crate is used to parse object file headers and contents. Very low-level support is used from this crate and almost all of it is disabled. Largely we're just using struct definitions as well as convenience methods internally to read bytes and such. * `addr2line` - this is the main meat of the implementation for symbolication. This crate depends on `gimli` for DWARF parsing and then provides interfaces needed by the `backtrace` crate to turn an address into a filename / line number. This crate is actually pretty small (fits in a single file almost!) and mirrors most of what `dwarf.c` does for libbacktrace. * `miniz_oxide` - the libbacktrace crate transparently handles compressed debug information which is compressed with zlib. This crate is used to decompress compressed debug sections. * `gimli` - not actually used directly, but a dependency of `addr2line`. * `adler32`- not used directly either, but a dependency of `miniz_oxide`. The goal of this change is to improve the safety of backtrace symbolication in the standard library, especially in the face of possibly malformed DWARF debug information. Even to this day we're still seeing segfaults in libbacktrace which could possibly become security vulnerabilities. This change should almost entirely eliminate this possibility whilc also paving the way forward to adding more features like split debug information. Some references for those interested are: * Original addition of libbacktrace - rust-lang#12602 * OOM with libbacktrace - rust-lang#24231 * Backtrace failure due to use of uninitialized value - rust-lang#28447 * Possibility to feed untrusted data to libbacktrace - rust-lang#21889 * Soundness fix for libbacktrace - rust-lang#33729 * Crash in libbacktrace - rust-lang#39468 * Support for macOS, never merged - ianlancetaylor/libbacktrace#2 * Performance issues with libbacktrace - rust-lang#29293, rust-lang#37477 * Update procedure is quite complicated due to how many patches we need to carry - rust-lang#50955 * Libbacktrace doesn't work on MinGW with dynamic libs - rust-lang#71060 * Segfault in libbacktrace on macOS - rust-lang#71397 Switching to Rust will not make us immune to all of these issues. The crashes are expected to go away, but correctness and performance may still have bugs arise. The gimli and `backtrace` crates, however, are actively maintained unlike libbacktrace, so this should enable us to at least efficiently apply fixes as situations come up. --- I want to note that my purpose for creating a PR here is to start a conversation about this. I think that all the various pieces are in place that this is compelling enough that I think this transition should be talked about seriously. There are a number of items which still need to be addressed before actually merging this PR, however: * [ ] `gimli` needs to be published to crates.io * [ ] `addr2line` needs a publish * [ ] `miniz_oxide` needs a publish * [ ] Tests probably shouldn't recommend the `gimli` crate's traits for implementing * [ ] The `backtrace` crate's branch changes need to be merged to the master branch (rust-lang/backtrace-rs#349) * [ ] The support for `libbacktrace` on some platforms needs to be audited to see if we should support more strategies in the gimli implementation - rust-lang/backtrace-rs#325, rust-lang/backtrace-rs#326, rust-lang/backtrace-rs#350, rust-lang/backtrace-rs#351 Most of the merging/publishing I'm not actively pushing on right now. It's a bit wonky for crates to support libstd so I'm holding off on pulling the trigger everywhere until there's a bit more discussion about how to go through with this. Namely rust-lang/backtrace-rs#349 I'm going to hold off merging until we decide to go through with the submodule strategy. In any case this is a pretty major change, so I suspect that the compiler team is likely going to be interested in this. I don't mean to force changes by dumping a bunch of code by any means. Integration of external crates into the standard library is so difficult I wanted to have a proof-of-concept to review while talking about whether to do this at all (hence the PR), but I'm more than happy to follow any processes needed to merge this. I must admit though that I'm not entirely sure myself at this time what the process would be to decide to merge this, so I'm hoping others can help me figure that out!
alexcrichton
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Jul 28, 2020
This commit is a proof-of-concept for switching the standard library's backtrace symbolication mechanism on most platforms from libbacktrace to gimli. The standard library's support for `RUST_BACKTRACE=1` requires in-process parsing of object files and DWARF debug information to interpret it and print the filename/line number of stack frames as part of a backtrace. Historically this support in the standard library has come from a library called "libbacktrace". The libbacktrace library seems to have been extracted from gcc at some point and is written in C. We've had a lot of issues with libbacktrace over time, unfortunately, though. The library does not appear to be actively maintained since we've had patches sit for months-to-years without comments. We have discovered a good number of soundness issues with the library itself, both when parsing valid DWARF as well as invalid DWARF. This is enough of an issue that the libs team has previously decided that we cannot feed untrusted inputs to libbacktrace. This also doesn't take into account the portability of libbacktrace which has been difficult to manage and maintain over time. While possible there are lots of exceptions and it's the main C dependency of the standard library right now. For years it's been the desire to switch over to a Rust-based solution for symbolicating backtraces. It's been assumed that we'll be using the Gimli family of crates for this purpose, which are targeted at safely and efficiently parsing DWARF debug information. I've been working recently to shore up the Gimli support in the `backtrace` crate. As of a few weeks ago the `backtrace` crate, by default, uses Gimli when loaded from crates.io. This transition has gone well enough that I figured it was time to start talking seriously about this change to the standard library. This commit is a preview of what's probably the best way to integrate the `backtrace` crate into the standard library with the Gimli feature turned on. While today it's used as a crates.io dependency, this commit switches the `backtrace` crate to a submodule of this repository which will need to be updated manually. This is not done lightly, but is thought to be the best solution. The primary reason for this is that the `backtrace` crate needs to do some pretty nontrivial filesystem interactions to locate debug information. Working without `std::fs` is not an option, and while it might be possible to do some sort of trait-based solution when prototyped it was found to be too unergonomic. Using a submodule allows the `backtrace` crate to build as a submodule of the `std` crate itself, enabling it to use `std::fs` and such. Otherwise this adds new dependencies to the standard library. This step requires extra attention because this means that these crates are now going to be included with all Rust programs by default. It's important to note, however, that we're already shipping libbacktrace with all Rust programs by default and it has a bunch of C code implementing all of this internally anyway, so we're basically already switching already-shipping functionality to Rust from C. * `object` - this crate is used to parse object file headers and contents. Very low-level support is used from this crate and almost all of it is disabled. Largely we're just using struct definitions as well as convenience methods internally to read bytes and such. * `addr2line` - this is the main meat of the implementation for symbolication. This crate depends on `gimli` for DWARF parsing and then provides interfaces needed by the `backtrace` crate to turn an address into a filename / line number. This crate is actually pretty small (fits in a single file almost!) and mirrors most of what `dwarf.c` does for libbacktrace. * `miniz_oxide` - the libbacktrace crate transparently handles compressed debug information which is compressed with zlib. This crate is used to decompress compressed debug sections. * `gimli` - not actually used directly, but a dependency of `addr2line`. * `adler32`- not used directly either, but a dependency of `miniz_oxide`. The goal of this change is to improve the safety of backtrace symbolication in the standard library, especially in the face of possibly malformed DWARF debug information. Even to this day we're still seeing segfaults in libbacktrace which could possibly become security vulnerabilities. This change should almost entirely eliminate this possibility whilc also paving the way forward to adding more features like split debug information. Some references for those interested are: * Original addition of libbacktrace - rust-lang#12602 * OOM with libbacktrace - rust-lang#24231 * Backtrace failure due to use of uninitialized value - rust-lang#28447 * Possibility to feed untrusted data to libbacktrace - rust-lang#21889 * Soundness fix for libbacktrace - rust-lang#33729 * Crash in libbacktrace - rust-lang#39468 * Support for macOS, never merged - ianlancetaylor/libbacktrace#2 * Performance issues with libbacktrace - rust-lang#29293, rust-lang#37477 * Update procedure is quite complicated due to how many patches we need to carry - rust-lang#50955 * Libbacktrace doesn't work on MinGW with dynamic libs - rust-lang#71060 * Segfault in libbacktrace on macOS - rust-lang#71397 Switching to Rust will not make us immune to all of these issues. The crashes are expected to go away, but correctness and performance may still have bugs arise. The gimli and `backtrace` crates, however, are actively maintained unlike libbacktrace, so this should enable us to at least efficiently apply fixes as situations come up.
Thomasdezeeuw
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Aug 21, 2020
Rust issue #71397 (rust-lang/rust#71397) has been resolved.
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I'm running macOS 10.15.3. Starting in the 3/26 nightly, running applications and tests that panic with RUST_BACKTRACE=1 frequently results in a segfault:
The backtrace from this shows libbacktrace:
Since 64a8c8a#diff-1a7024d46c31d728a04d5e0cafd98df8 merged as part of #70383 which merged on March 25, there's a pretty clear candidate for the regression.
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