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Check for invalid sstatus values in set_mcontext().

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Previously, this check was only in sys_sigreturn() which meant that
user applications could write invalid values to the register via
setcontext() or swapcontext().

Reviewed by:	mhorne
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D23219
This commit is contained in:
John Baldwin 2020-01-17 19:13:49 +00:00
parent ffbf0e3ce4
commit 7f1c5f3604
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=356840
1 changed files with 8 additions and 10 deletions
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18
sys/riscv/riscv/machdep.c
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@ -367,6 +367,14 @@ set_mcontext(struct thread *td, mcontext_t *mcp)
tf = td->td_frame;
/*
* Make sure the processor mode has not been tampered with and
* interrupts have not been disabled.
* Supervisor interrupts in user mode are always enabled.
*/
if ((mcp->mc_gpregs.gp_sstatus & SSTATUS_SPP) != 0)
return (EINVAL);
memcpy(tf->tf_t, mcp->mc_gpregs.gp_t, sizeof(tf->tf_t));
memcpy(tf->tf_s, mcp->mc_gpregs.gp_s, sizeof(tf->tf_s));
memcpy(tf->tf_a, mcp->mc_gpregs.gp_a, sizeof(tf->tf_a));
@ -523,22 +531,12 @@ struct sigreturn_args {
int
sys_sigreturn(struct thread *td, struct sigreturn_args *uap)
{
uint64_t sstatus;
ucontext_t uc;
int error;
if (copyin(uap->sigcntxp, &uc, sizeof(uc)))
return (EFAULT);
/*
* Make sure the processor mode has not been tampered with and
* interrupts have not been disabled.
* Supervisor interrupts in user mode are always enabled.
*/
sstatus = uc.uc_mcontext.mc_gpregs.gp_sstatus;
if ((sstatus & SSTATUS_SPP) != 0)
return (EINVAL);
error = set_mcontext(td, &uc.uc_mcontext);
if (error != 0)
return (error);