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Don't check %cs *after* it has being set in sigreturn. If the check 

fails, applications could end up running in kernel mode (oops).

Submitted by: bde
This commit is contained in:
Marcel Moolenaar 1999-10-01 07:22:50 +00:00
parent 0f25802642
commit eb9df38223
2 changed files with 12 additions and 10 deletions
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11
sys/amd64/amd64/machdep.c
View File

@ -884,7 +884,7 @@ sigreturn(p, uap)
struct trapframe *regs;
ucontext_t *ucp;
struct sigframe *sfp;
int eflags;
int cs, eflags;
regs = p->p_md.md_regs;
ucp = uap->sigcntxp;
@ -947,18 +947,19 @@ sigreturn(p, uap)
return(EINVAL);
}
*regs = ucp->uc_mcontext.mc_tf;
/*
* Don't allow users to load a valid privileged %cs. Let the
* hardware check for invalid selectors, excess privilege in
* other selectors, invalid %eip's and invalid %esp's.
*/
if (!CS_SECURE(regs->tf_cs)) {
printf("sigreturn: cs = 0x%x\n", regs->tf_cs);
cs = ucp->uc_mcontext.mc_tf.tf_cs;
if (!CS_SECURE(cs)) {
printf("sigreturn: cs = 0x%x\n", cs);
trapsignal(p, SIGBUS, T_PROTFLT);
return(EINVAL);
}
*regs = ucp->uc_mcontext.mc_tf;
}
p->p_sigacts->ps_sigstk = ucp->uc_stack;

11
sys/i386/i386/machdep.c
View File

@ -884,7 +884,7 @@ sigreturn(p, uap)
struct trapframe *regs;
ucontext_t *ucp;
struct sigframe *sfp;
int eflags;
int cs, eflags;
regs = p->p_md.md_regs;
ucp = uap->sigcntxp;
@ -947,18 +947,19 @@ sigreturn(p, uap)
return(EINVAL);
}
*regs = ucp->uc_mcontext.mc_tf;
/*
* Don't allow users to load a valid privileged %cs. Let the
* hardware check for invalid selectors, excess privilege in
* other selectors, invalid %eip's and invalid %esp's.
*/
if (!CS_SECURE(regs->tf_cs)) {
printf("sigreturn: cs = 0x%x\n", regs->tf_cs);
cs = ucp->uc_mcontext.mc_tf.tf_cs;
if (!CS_SECURE(cs)) {
printf("sigreturn: cs = 0x%x\n", cs);
trapsignal(p, SIGBUS, T_PROTFLT);
return(EINVAL);
}
*regs = ucp->uc_mcontext.mc_tf;
}
p->p_sigacts->ps_sigstk = ucp->uc_stack;