From 161a438d730dade2ba2b1bf8785f0759aba4ca5f Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 20 Oct 2022 10:39:08 +0200 Subject: efi: random: reduce seed size to 32 bytes We no longer need at least 64 bytes of random seed to permit the early crng init to complete. The RNG is now based on Blake2s, so reduce the EFI seed size to the Blake2s hash size, which is sufficient for our purposes. While at it, drop the READ_ONCE(), which was supposed to prevent size from being evaluated after seed was unmapped. However, this cannot actually happen, so READ_ONCE() is unnecessary here. Cc: # v4.14+ Signed-off-by: Ard Biesheuvel Reviewed-by: Jason A. Donenfeld Acked-by: Ilias Apalodimas --- include/linux/efi.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/efi.h b/include/linux/efi.h index 80f3c1c7827d..929d559ad41d 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1222,7 +1222,7 @@ efi_status_t efi_random_get_seed(void); arch_efi_call_virt_teardown(); \ }) -#define EFI_RANDOM_SEED_SIZE 64U +#define EFI_RANDOM_SEED_SIZE 32U // BLAKE2S_HASH_SIZE struct linux_efi_random_seed { u32 size; -- cgit v1.2.3 From 6f7630b1b5bc672b54c1285ee6aba752b446672c Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 28 Oct 2022 15:32:07 -0700 Subject: fortify: Capture __bos() results in const temp vars In two recent run-time memcpy() bound checking bug reports (NFS[1] and JFS[2]), the _detection_ was working correctly (in the sense that the requested copy size was larger than the destination field size), but the _warning text_ was showing the destination field size as SIZE_MAX ("unknown size"). This should be impossible, since the detection function will explicitly give up if the destination field size is unknown. For example, the JFS warning was: memcpy: detected field-spanning write (size 132) of single field "ip->i_link" at fs/jfs/namei.c:950 (size 18446744073709551615) Other cases of this warning (e.g.[3]) have reported correctly, and the reproducer only happens under GCC (at least 10.2 and 12.1), so this currently appears to be a GCC bug. Explicitly capturing the __builtin_object_size() results in const temporary variables fixes the report. For example, the JFS reproducer now correctly reports the field size (128): memcpy: detected field-spanning write (size 132) of single field "ip->i_link" at fs/jfs/namei.c:950 (size 128) Examination of the .text delta (which is otherwise identical), shows the literal value used in the report changing: - mov $0xffffffffffffffff,%rcx + mov $0x80,%ecx [1] https://lore.kernel.org/lkml/Y0zEzZwhOxTDcBTB@codemonkey.org.uk/ [2] https://syzkaller.appspot.com/bug?id=23d613df5259b977dac1696bec77f61a85890e3d [3] https://lore.kernel.org/all/202210110948.26b43120-yujie.liu@intel.com/ Cc: "Dr. David Alan Gilbert" Cc: llvm@lists.linux.dev Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook --- include/linux/fortify-string.h | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index 4029fe368a4f..0f00a551939a 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -441,13 +441,18 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ p_size_field, q_size_field, op) ({ \ - size_t __fortify_size = (size_t)(size); \ - WARN_ONCE(fortify_memcpy_chk(__fortify_size, p_size, q_size, \ - p_size_field, q_size_field, #op), \ + const size_t __fortify_size = (size_t)(size); \ + const size_t __p_size = (p_size); \ + const size_t __q_size = (q_size); \ + const size_t __p_size_field = (p_size_field); \ + const size_t __q_size_field = (q_size_field); \ + WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \ + __q_size, __p_size_field, \ + __q_size_field, #op), \ #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \ __fortify_size, \ "field \"" #p "\" at " __FILE__ ":" __stringify(__LINE__), \ - p_size_field); \ + __p_size_field); \ __underlying_##op(p, q, __fortify_size); \ }) -- cgit v1.2.3