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x86/uprobes: Keep shadow stack in sync for emulated CALLs

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Uprobe CALL emulation updates the normal user stack, but not the CET user
shadow stack. The subsequent RET then sees a stale shadow stack entry and
raises #CP.

Update the relative CALL emulation and XOL CALL fixup paths to keep the
shadow stack in sync.

Fixes: 488af8ea71 ("x86/shstk: Wire in shadow stack interface")
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Link: https://patch.msgid.link/8b5b1c7407b98f31664ad7b6a6faf20d2d4a6cad.1782777969.git.dwindsor@gmail.com
This commit is contained in:
David Windsor 2026-06-29 20:13:33 -04:00 committed by Peter Zijlstra
parent 037a3c43ed
commit abf08854d2
1 changed files with 11 additions and 1 deletions
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12
arch/x86/kernel/uprobes.c
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@ -1246,9 +1246,15 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs
long correction = utask->vaddr - utask->xol_vaddr;
regs->ip += correction;
} else if (auprobe->defparam.fixups & UPROBE_FIX_CALL) {
unsigned long retaddr = utask->vaddr + auprobe->defparam.ilen;
int err;
regs->sp += sizeof_long(regs); /* Pop incorrect return address */
if (emulate_push_stack(regs, utask->vaddr + auprobe->defparam.ilen))
if (emulate_push_stack(regs, retaddr))
return -ERESTART;
err = shstk_update_last_frame(retaddr);
if (err)
return err;
}
/* popf; tell the caller to not touch TF */
if (auprobe->defparam.fixups & UPROBE_FIX_SETF)
@ -1338,6 +1344,10 @@ static bool branch_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
*/
if (emulate_push_stack(regs, new_ip))
return false;
if (shstk_push(new_ip) == -EFAULT) {
regs->sp += sizeof_long(regs);
return false;
}
} else if (!check_jmp_cond(auprobe, regs)) {
offs = 0;
}