Fix the issue further discussed in: 1. https://lore.kernel.org/linux-sgx/op.0rwbv916wjvjmi@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ 2. https://lore.kernel.org/linux-sgx/20201003195440.GD20115@xxxxxxxxxxxxxxxxxxxx/ Reported-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx> Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Cc: Jethro Beekman <jethro@xxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> --- v3: * Added the missing unlock pointed out by Matthew. * Tested with the correct patch (last time had v1 applied) * I don't know what happened to v2 changelog, checked from patchwork and it wasn't there. Hope this is not scraped. arch/x86/kernel/cpu/sgx/encl.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index 4c6407cd857a..e91e521b03a8 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -307,6 +307,8 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start, unsigned long idx_start = PFN_DOWN(start); unsigned long idx_end = PFN_DOWN(end - 1); struct sgx_encl_page *page; + unsigned long count = 0; + int ret = 0; XA_STATE(xas, &encl->page_array, idx_start); @@ -317,11 +319,30 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start, if (current->personality & READ_IMPLIES_EXEC) return -EACCES; - xas_for_each(&xas, page, idx_end) - if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) - return -EACCES; + /* + * No need to hold encl->lock: + * 1. None of the page->* get written. + * 2. page->vm_max_prot_bits is set in sgx_encl_page_alloc(). This + * is before calling xa_insert(). After that it is never modified. + */ + xas_lock(&xas); + xas_for_each(&xas, page, idx_end) { + if (++count % XA_CHECK_SCHED) + continue; - return 0; + if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) { + ret = -EACCES; + break; + } + + xas_pause(&xas); + xas_unlock(&xas); + cond_resched(); + xas_lock(&xas); + } + xas_unlock(&xas); + + return ret; } static int sgx_vma_mprotect(struct vm_area_struct *vma, -- 2.25.1
