From: Alexei Starovoitov ast@kernel.org
commit d319f344561de23e810515d109c7278919bff7b0 upstream.
There are several issues with copy_from_user_nofault():
- access_ok() is designed for user context only and for that reason it has WARN_ON_IN_IRQ() which triggers when bpf, kprobe, eprobe and perf on ppc are calling it from irq.
- it's missing nmi_uaccess_okay() which is a nop on all architectures except x86 where it's required. The comment in arch/x86/mm/tlb.c explains the details why it's necessary. Calling copy_from_user_nofault() from bpf, [ke]probe without this check is not safe.
- __copy_from_user_inatomic() under CONFIG_HARDENED_USERCOPY is calling check_object_size()->__check_object_size()->check_heap_object()->find_vmap_area()->spin_lock() which is not safe to do from bpf, [ke]probe and perf due to potential deadlock.
Fix all three issues. At the end the copy_from_user_nofault() becomes equivalent to copy_from_user_nmi() from safety point of view with a difference in the return value.
Reported-by: Hsin-Wei Hung hsinweih@uci.edu Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Florian Lehner dev@der-flo.net Tested-by: Hsin-Wei Hung hsinweih@uci.edu Tested-by: Florian Lehner dev@der-flo.net Link: https://lore.kernel.org/r/20230410174345.4376-2-dev@der-flo.net Signed-off-by: Alexei Starovoitov ast@kernel.org Cc: Javier Honduvilla Coto javierhonduco@gmail.com Cc: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/maccess.c | 16 +++++++++++----- mm/usercopy.c | 2 +- 2 files changed, 12 insertions(+), 6 deletions(-)
--- a/mm/maccess.c +++ b/mm/maccess.c @@ -5,6 +5,7 @@ #include <linux/export.h> #include <linux/mm.h> #include <linux/uaccess.h> +#include <asm/tlb.h>
bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) @@ -113,11 +114,16 @@ Efault: long copy_from_user_nofault(void *dst, const void __user *src, size_t size) { long ret = -EFAULT; - if (access_ok(src, size)) { - pagefault_disable(); - ret = __copy_from_user_inatomic(dst, src, size); - pagefault_enable(); - } + + if (!__access_ok(src, size)) + return ret; + + if (!nmi_uaccess_okay()) + return ret; + + pagefault_disable(); + ret = __copy_from_user_inatomic(dst, src, size); + pagefault_enable();
if (ret) return -EFAULT; --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -173,7 +173,7 @@ static inline void check_heap_object(con return; }
- if (is_vmalloc_addr(ptr)) { + if (is_vmalloc_addr(ptr) && !pagefault_disabled()) { struct vmap_area *area = find_vmap_area(addr);
if (!area)