header.y: initialize body YYSTYPE for empty and TEXT - #8
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The body nonterminal is a char *. With a mid-rule action on the TEXT
alternative, Bison does not apply the default "$$ = $1", so $$ was left
uninitialized. The empty alternative had no action at all.
RFC 5322 folded headers such as
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* 0.7 ...
parse as (empty body) followed by one or more WRAP tokens. Using the
garbage $$ from the empty production as $1 in "body WRAP" then crashes
in strlen/printf on architectures where the stack is not coincidentally
zero (observed on RISC-V; often masked on x86).
Set $$ = NULL for an empty body and $$ = $1 for TEXT, and guard the
WRAP concatenation against NULL the same way.
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The body nonterminal is a char *. With a mid-rule action on the TEXT alternative, Bison does not apply the default "$$ =$1", so $ $ was left uninitialized. The empty alternative had no action at all.
RFC 5322 folded headers such as
parse as (empty body) followed by one or more WRAP tokens. Using the garbage $$ from the empty production as $1 in "body WRAP" then crashes in strlen/printf on architectures where the stack is not coincidentally zero (observed on RISC-V; often masked on x86).
Set $$ = NULL for an empty body and $$ = $1 for TEXT, and guard the WRAP concatenation against NULL the same way.