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Message-ID: <YySML2HfqaE/wXBU@casper.infradead.org> Date: Fri, 16 Sep 2022 15:46:07 +0100 From: Matthew Wilcox <willy@...radead.org> To: Kees Cook <keescook@...omium.org> Cc: Uladzislau Rezki <urezki@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Yu Zhao <yuzhao@...gle.com>, dev@...-flo.net, linux-mm@...ck.org, linux-hardening@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org, x86@...nel.org, linux-perf-users@...r.kernel.org, linux-arch@...r.kernel.org Subject: Re: [PATCH 3/3] usercopy: Add find_vmap_area_try() to avoid deadlocks On Fri, Sep 16, 2022 at 06:59:57AM -0700, Kees Cook wrote: > The check_object_size() checks under CONFIG_HARDENED_USERCOPY need to be > more defensive against running from interrupt context. Use a best-effort > check for VMAP areas when running in interrupt context I had something more like this in mind: diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 096d48aa3437..2b7c52e76856 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -215,7 +215,7 @@ extern struct vm_struct *__get_vm_area_caller(unsigned long size, void free_vm_area(struct vm_struct *area); extern struct vm_struct *remove_vm_area(const void *addr); extern struct vm_struct *find_vm_area(const void *addr); -struct vmap_area *find_vmap_area(unsigned long addr); +struct vmap_area *find_vmap_area_try(unsigned long addr); static inline bool is_vm_area_hugepages(const void *addr) { diff --git a/mm/usercopy.c b/mm/usercopy.c index c1ee15a98633..e0fb605c1b38 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -173,7 +173,11 @@ static inline void check_heap_object(const void *ptr, unsigned long n, } if (is_vmalloc_addr(ptr)) { - struct vmap_area *area = find_vmap_area(addr); + struct vmap_area *area = find_vmap_area_try(addr); + + /* We may be in NMI context */ + if (area == ERR_PTR(-EAGAIN)) + return; if (!area) usercopy_abort("vmalloc", "no area", to_user, 0, n); diff --git a/mm/vmalloc.c b/mm/vmalloc.c index dd6cdb201195..2ea76cb56d4b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1829,7 +1829,7 @@ static void free_unmap_vmap_area(struct vmap_area *va) free_vmap_area_noflush(va); } -struct vmap_area *find_vmap_area(unsigned long addr) +static struct vmap_area *find_vmap_area(unsigned long addr) { struct vmap_area *va; @@ -1840,6 +1840,18 @@ struct vmap_area *find_vmap_area(unsigned long addr) return va; } +struct vmap_area *find_vmap_area_try(unsigned long addr) +{ + struct vmap_area *va; + + if (!spin_lock(&vmap_area_lock)) + return ERR_PTR(-EAGAIN); + va = __find_vmap_area(addr, &vmap_area_root); + spin_unlock(&vmap_area_lock); + + return va; +} + /*** Per cpu kva allocator ***/ /*
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