* Crash when detached thread exits with bionic and QEMU usermode
@ 2020-05-15 18:09 Michael Goffioul
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From: Michael Goffioul @ 2020-05-15 18:09 UTC (permalink / raw
To: QEMU Developers
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Not sure this is a bug in QEMU usermode, but I've tracked a crash that
happens when running ARM guest code linked against bionic (from Android).
More specifically when a detached thread exits.
In bionic, threads are created with the flag CLONE_CHILD_CLEARTID [1]. When
a detached thread exits normally, bionic calls set_tid_address with nullptr
to reset the address, before unmapping the thread memory [2] and exiting.
The problem seems to be that the handling of TARGET_NR_set_tid_address does
not reset TaskState->child_tidptr, and this lead to a SIGSEGV during
handling of TARGET_NR_exit [3]
[1]
https://github.com/aosp-mirror/platform_bionic/blob/android-10.0.0_r33/libc/bionic/pthread_create.cpp#L390
[2]
https://github.com/aosp-mirror/platform_bionic/blob/android-10.0.0_r33/libc/bionic/pthread_exit.cpp#L123
[3] https://github.com/qemu/qemu/blob/master/linux-user/syscall.c#L7650
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2020-05-15 18:09 Crash when detached thread exits with bionic and QEMU usermode Michael Goffioul
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