Commit 94234941 authored by Benjamin Berg's avatar Benjamin Berg Committed by Johannes Berg
Browse files

um: fix SECCOMP 32bit xstate register restore 



There was a typo that caused the extended FP state to be copied into the
wrong location on 32 bit. On 32 bit we only store the xstate internally
as that already contains everything. However, for compatibility, the
mcontext on 32 bit first contains the legacy FP state and then the
xstate.

The code copied the xstate on top of the legacy FP state instead of
using the correct offset. This offset was already calculated in the
xstate_* variables, so simply switch to those to fix the problem.

With this SECCOMP mode works on 32 bit, so lift the restriction.

Fixes: b1e1bd2e ("um: Add helper functions to get/set state for SECCOMP")
Signed-off-by: default avatarBenjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250604081705.934112-1-benjamin@sipsolutions.net


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent e92e2552

arch/um/os-Linux/start_up.c

+0 −4
Original line number Diff line number Diff line
@@ -296,10 +296,6 @@ static bool __init init_seccomp(void) 
	int n;

	unsigned long sp;



	/* doesn't work on 32-bit right now */

	if (!IS_ENABLED(CONFIG_64BIT))

		return false;



	/*

	 * We check that we can install a seccomp filter and then exit(0)

	 * from a trapped syscall.

arch/x86/um/os-Linux/mcontext.c

+1 −1
Original line number Diff line number Diff line
@@ -231,7 +231,7 @@ int set_stub_state(struct uml_pt_regs *regs, struct stub_data *data, 
	xstate_size = fp_size;

#endif



	memcpy(fpstate_stub, &regs->fp, fp_size);

	memcpy(xstate_stub, &regs->fp, xstate_size);



#ifdef __i386__

	/*