user/sven/linux.git/mm/usercopy.c, branch v4.9.147

mm: usercopy: Check for module addresses

2016-09-20T23:07:39Z

While running a compile on arm64, I hit a memory exposure usercopy: kernel memory exposure attempt detected from fffffc0000f3b1a8 (buffer_head) (1 bytes) ------------[ cut here ]------------ kernel BUG at mm/usercopy.c:75! Internal error: Oops - BUG: 0 [#1] SMP Modules linked in: ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_broute bridge stp llc ebtable_nat ip6table_security ip6table_raw ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle iptable_security iptable_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle ebtable_filter ebtables ip6table_filter ip6_tables vfat fat xgene_edac xgene_enet edac_core i2c_xgene_slimpro i2c_core at803x realtek xgene_dma mdio_xgene gpio_dwapb gpio_xgene_sb xgene_rng mailbox_xgene_slimpro nfsd auth_rpcgss nfs_acl lockd grace sunrpc xfs libcrc32c sdhci_of_arasan sdhci_pltfm sdhci mmc_core xhci_plat_hcd gpio_keys CPU: 0 PID: 19744 Comm: updatedb Tainted: G W 4.8.0-rc3-threadinfo+ #1 Hardware name: AppliedMicro X-Gene Mustang Board/X-Gene Mustang Board, BIOS 3.06.12 Aug 12 2016 task: fffffe03df944c00 task.stack: fffffe00d128c000 PC is at __check_object_size+0x70/0x3f0 LR is at __check_object_size+0x70/0x3f0 ... [] __check_object_size+0x70/0x3f0 [] filldir64+0x158/0x1a0 [] __fat_readdir+0x4a0/0x558 [fat] [] fat_readdir+0x34/0x40 [fat] [] iterate_dir+0x190/0x1e0 [] SyS_getdents64+0x88/0x120 [] el0_svc_naked+0x24/0x28 fffffc0000f3b1a8 is a module address. Modules may have compiled in strings which could get copied to userspace. In this instance, it looks like "." which matches with a size of 1 byte. Extend the is_vmalloc_addr check to be is_vmalloc_or_module_addr to cover all possible cases. Signed-off-by: Laura Abbott Signed-off-by: Kees Cook

usercopy: remove page-spanning test for now

2016-09-07T18:33:26Z

A custom allocator without __GFP_COMP that copies to userspace has been found in vmw_execbuf_process[1], so this disables the page-span checker by placing it behind a CONFIG for future work where such things can be tracked down later. [1] https://bugzilla.redhat.com/show_bug.cgi?id=1373326 Reported-by: Vinson Lee Fixes: f5509cc18daa ("mm: Hardened usercopy") Signed-off-by: Kees Cook

usercopy: fix overlap check for kernel text

2016-08-23T02:10:51Z

When running with a local patch which moves the '_stext' symbol to the very beginning of the kernel text area, I got the following panic with CONFIG_HARDENED_USERCOPY: usercopy: kernel memory exposure attempt detected from ffff88103dfff000 () (4096 bytes) ------------[ cut here ]------------ kernel BUG at mm/usercopy.c:79! invalid opcode: 0000 [#1] SMP ... CPU: 0 PID: 4800 Comm: cp Not tainted 4.8.0-rc3.after+ #1 Hardware name: Dell Inc. PowerEdge R720/0X3D66, BIOS 2.5.4 01/22/2016 task: ffff880817444140 task.stack: ffff880816274000 RIP: 0010:[] __check_object_size+0x76/0x413 RSP: 0018:ffff880816277c40 EFLAGS: 00010246 RAX: 000000000000006b RBX: ffff88103dfff000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff88081f80dfa8 RDI: ffff88081f80dfa8 RBP: ffff880816277c90 R08: 000000000000054c R09: 0000000000000000 R10: 0000000000000005 R11: 0000000000000006 R12: 0000000000001000 R13: ffff88103e000000 R14: ffff88103dffffff R15: 0000000000000001 FS: 00007fb9d1750800(0000) GS:ffff88081f800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000021d2000 CR3: 000000081a08f000 CR4: 00000000001406f0 Stack: ffff880816277cc8 0000000000010000 000000043de07000 0000000000000000 0000000000001000 ffff880816277e60 0000000000001000 ffff880816277e28 000000000000c000 0000000000001000 ffff880816277ce8 ffffffff8136c3a6 Call Trace: [] copy_page_to_iter_iovec+0xa6/0x1c0 [] copy_page_to_iter+0x16/0x90 [] generic_file_read_iter+0x3e3/0x7c0 [] ? xfs_file_buffered_aio_write+0xad/0x260 [xfs] [] ? down_read+0x12/0x40 [] xfs_file_buffered_aio_read+0x51/0xc0 [xfs] [] xfs_file_read_iter+0x62/0xb0 [xfs] [] __vfs_read+0xdf/0x130 [] vfs_read+0x8e/0x140 [] SyS_read+0x55/0xc0 [] do_syscall_64+0x67/0x160 [] entry_SYSCALL64_slow_path+0x25/0x25 RIP: 0033:[<00007fb9d0c33c00>] 0x7fb9d0c33c00 RSP: 002b:00007ffc9c262f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: fffffffffff8ffff RCX: 00007fb9d0c33c00 RDX: 0000000000010000 RSI: 00000000021c3000 RDI: 0000000000000004 RBP: 00000000021c3000 R08: 0000000000000000 R09: 00007ffc9c264d6c R10: 00007ffc9c262c50 R11: 0000000000000246 R12: 0000000000010000 R13: 00007ffc9c2630b0 R14: 0000000000000004 R15: 0000000000010000 Code: 81 48 0f 44 d0 48 c7 c6 90 4d a3 81 48 c7 c0 bb b3 a2 81 48 0f 44 f0 4d 89 e1 48 89 d9 48 c7 c7 68 16 a3 81 31 c0 e8 f4 57 f7 ff <0f> 0b 48 8d 90 00 40 00 00 48 39 d3 0f 83 22 01 00 00 48 39 c3 RIP [] __check_object_size+0x76/0x413 RSP The checked object's range [ffff88103dfff000, ffff88103e000000) is valid, so there shouldn't have been a BUG. The hardened usercopy code got confused because the range's ending address is the same as the kernel's text starting address at 0xffff88103e000000. The overlap check is slightly off. Fixes: f5509cc18daa ("mm: Hardened usercopy") Signed-off-by: Josh Poimboeuf Signed-off-by: Kees Cook

usercopy: avoid potentially undefined behavior in pointer math

2016-08-23T02:07:55Z

check_bogus_address() checked for pointer overflow using this expression, where 'ptr' has type 'const void *': ptr + n < ptr Since pointer wraparound is undefined behavior, gcc at -O2 by default treats it like the following, which would not behave as intended: (long)n < 0 Fortunately, this doesn't currently happen for kernel code because kernel code is compiled with -fno-strict-overflow. But the expression should be fixed anyway to use well-defined integer arithmetic, since it could be treated differently by different compilers in the future or could be reported by tools checking for undefined behavior. Signed-off-by: Eric Biggers Signed-off-by: Kees Cook

mm: Hardened usercopy

2016-07-26T21:41:47Z

This is the start of porting PAX_USERCOPY into the mainline kernel. This is the first set of features, controlled by CONFIG_HARDENED_USERCOPY. The work is based on code by PaX Team and Brad Spengler, and an earlier port from Casey Schaufler. Additional non-slab page tests are from Rik van Riel. This patch contains the logic for validating several conditions when performing copy_to_user() and copy_from_user() on the kernel object being copied to/from: - address range doesn't wrap around - address range isn't NULL or zero-allocated (with a non-zero copy size) - if on the slab allocator: - object size must be less than or equal to copy size (when check is implemented in the allocator, which appear in subsequent patches) - otherwise, object must not span page allocations (excepting Reserved and CMA ranges) - if on the stack - object must not extend before/after the current process stack - object must be contained by a valid stack frame (when there is arch/build support for identifying stack frames) - object must not overlap with kernel text Signed-off-by: Kees Cook Tested-by: Valdis Kletnieks Tested-by: Michael Ellerman