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kernel
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avoid race condition that could corrupt user stack if DOS re-entered too soon 

apply suggested fix from SF bug 215 (https://sourceforge.net/p/freedos/bugs/215/), InDOS cleared but small chance DOS re-entered before user stack restored thus corrupting user stack
This commit is contained in:
Kenneth J Davis 2024-08-19 16:31:22 -04:00
parent dabfaf7d54
commit 1cc00e194d
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1 changed files with 5 additions and 1 deletions
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6
kernel/entry.asm
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@ -406,7 +406,7 @@ int21_normalentry:
push bp
call _int21_service
int21_exit: dec byte [_InDOS]
int21_exit:
%IFDEF WIN31SUPPORT
call end_dos_crit_sect ; release all critical sections
%if 0
@ -417,6 +417,10 @@ int21_exit: dec byte [_InDOS]
%endif
%ENDIF ; WIN31SUPPORT
; tiny chance DOS re-entered between clearing InDOS and restoring user stack,
; so we disable interrupts until user stack restored; see SF bug# 215
cli
dec byte [_InDOS]
;
; Recover registers from system call. Registers and flags
; were modified by the system call.