{19486} arch/arm: set PSPLIM to top of TLS region to protect it from overflow - #19634
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A crash was observed when running ps: a BusFault in nxtask_argvstr dereferencing tl_argv, because a thread's stack overflow had silently corrupted the TLS region where tl_argv resides. On ARMv8-M with CONFIG_ARMV8M_STACKCHECK_HARDWARE, PSPLIM was set to stack_alloc_ptr -- the bottom of the allocation where TLS begins. The stack grows downward and TLS occupies [stack_alloc_ptr, stack_alloc_ptr + tls_info_size()), so an overflow crossed into TLS and clobbered tl_argv before SP reached the limit, going undetected until code that read the corrupted TLS data (such as ps) hit the bad pointer. Set the limit to stack_alloc_ptr + tls_info_size() -- the top of the TLS region and the usable stack base -- so an overflow faults at the TLS boundary, before any TLS byte is touched. Include <tls/tls.h> for the tls_info_size() macro, which is the value sched reserves for the TLS region via up_stack_frame(). Signed-off-by: Junbo Zheng <zhengjunbo1@xiaomi.com>
jerpelea
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acassis,
cederom,
linguini1,
lupyuen and
xiaoxiang781216
August 3, 2026 09:55
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cederom
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Aug 3, 2026
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Summary
A crash was observed when running ps: a BusFault in nxtask_argvstr dereferencing tl_argv, because a thread's stack overflow had silently corrupted the TLS region where tl_argv resides.
On ARMv8-M with CONFIG_ARMV8M_STACKCHECK_HARDWARE, PSPLIM was set to stack_alloc_ptr -- the bottom of the allocation where TLS begins. The stack grows downward and TLS occupies [stack_alloc_ptr, stack_alloc_ptr
Set the limit to stack_alloc_ptr + tls_info_size() -- the top of the TLS region and the usable stack base -- so an overflow faults at the TLS boundary, before any TLS byte is touched. Include <tls/tls.h> for the tls_info_size() macro, which is the value sched reserves for the TLS region via up_stack_frame().
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