From ecb4534b6a1c8a9c01d4d1d532d58fc18f23c8da Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Wed, 26 Jul 2023 12:08:28 -0700 Subject: af_unix: Terminate sun_path when bind()ing pathname socket. kernel test robot reported slab-out-of-bounds access in strlen(). [0] Commit 06d4c8a80836 ("af_unix: Fix fortify_panic() in unix_bind_bsd().") removed unix_mkname_bsd() call in unix_bind_bsd(). If sunaddr->sun_path is not terminated by user and we don't enable CONFIG_INIT_STACK_ALL_ZERO=y, strlen() will do the out-of-bounds access during file creation. Let's go back to strlen()-with-sockaddr_storage way and pack all 108 trickiness into unix_mkname_bsd() with bold comments. [0]: BUG: KASAN: slab-out-of-bounds in strlen (lib/string.c:?) Read of size 1 at addr ffff000015492777 by task fortify_strlen_/168 CPU: 0 PID: 168 Comm: fortify_strlen_ Not tainted 6.5.0-rc1-00333-g3329b603ebba #16 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace (arch/arm64/kernel/stacktrace.c:235) show_stack (arch/arm64/kernel/stacktrace.c:242) dump_stack_lvl (lib/dump_stack.c:107) print_report (mm/kasan/report.c:365 mm/kasan/report.c:475) kasan_report (mm/kasan/report.c:590) __asan_report_load1_noabort (mm/kasan/report_generic.c:378) strlen (lib/string.c:?) getname_kernel (./include/linux/fortify-string.h:? fs/namei.c:226) kern_path_create (fs/namei.c:3926) unix_bind (net/unix/af_unix.c:1221 net/unix/af_unix.c:1324) __sys_bind (net/socket.c:1792) __arm64_sys_bind (net/socket.c:1801) invoke_syscall (arch/arm64/kernel/syscall.c:? arch/arm64/kernel/syscall.c:52) el0_svc_common (./include/linux/thread_info.h:127 arch/arm64/kernel/syscall.c:147) do_el0_svc (arch/arm64/kernel/syscall.c:189) el0_svc (./arch/arm64/include/asm/daifflags.h:28 arch/arm64/kernel/entry-common.c:133 arch/arm64/kernel/entry-common.c:144 arch/arm64/kernel/entry-common.c:648) el0t_64_sync_handler (arch/arm64/kernel/entry-common.c:?) el0t_64_sync (arch/arm64/kernel/entry.S:591) Allocated by task 168: kasan_set_track (mm/kasan/common.c:45 mm/kasan/common.c:52) kasan_save_alloc_info (mm/kasan/generic.c:512) __kasan_kmalloc (mm/kasan/common.c:383) __kmalloc (mm/slab_common.c:? mm/slab_common.c:998) unix_bind (net/unix/af_unix.c:257 net/unix/af_unix.c:1213 net/unix/af_unix.c:1324) __sys_bind (net/socket.c:1792) __arm64_sys_bind (net/socket.c:1801) invoke_syscall (arch/arm64/kernel/syscall.c:? arch/arm64/kernel/syscall.c:52) el0_svc_common (./include/linux/thread_info.h:127 arch/arm64/kernel/syscall.c:147) do_el0_svc (arch/arm64/kernel/syscall.c:189) el0_svc (./arch/arm64/include/asm/daifflags.h:28 arch/arm64/kernel/entry-common.c:133 arch/arm64/kernel/entry-common.c:144 arch/arm64/kernel/entry-common.c:648) el0t_64_sync_handler (arch/arm64/kernel/entry-common.c:?) el0t_64_sync (arch/arm64/kernel/entry.S:591) The buggy address belongs to the object at ffff000015492700 which belongs to the cache kmalloc-128 of size 128 The buggy address is located 0 bytes to the right of allocated 119-byte region [ffff000015492700, ffff000015492777) The buggy address belongs to the physical page: page:00000000aeab52ba refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x55492 anon flags: 0x3fffc0000000200(slab|node=0|zone=0|lastcpupid=0xffff) page_type: 0xffffffff() raw: 03fffc0000000200 ffff0000084018c0 fffffc00003d0e00 0000000000000005 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff000015492600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff000015492680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff000015492700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 07 fc ^ ffff000015492780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff000015492800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb Fixes: 06d4c8a80836 ("af_unix: Fix fortify_panic() in unix_bind_bsd().") Reported-by: kernel test robot Closes: https://lore.kernel.org/netdev/202307262110.659e5e8-oliver.sang@intel.com/ Signed-off-by: Kuniyuki Iwashima Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20230726190828.47874-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni --- net/unix/af_unix.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) (limited to 'net/unix/af_unix.c') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index bbacf4c60fe3..78585217f61a 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -289,17 +289,29 @@ static int unix_validate_addr(struct sockaddr_un *sunaddr, int addr_len) return 0; } -static void unix_mkname_bsd(struct sockaddr_un *sunaddr, int addr_len) +static int unix_mkname_bsd(struct sockaddr_un *sunaddr, int addr_len) { + struct sockaddr_storage *addr = (struct sockaddr_storage *)sunaddr; + short offset = offsetof(struct sockaddr_storage, __data); + + BUILD_BUG_ON(offset != offsetof(struct sockaddr_un, sun_path)); + /* This may look like an off by one error but it is a bit more * subtle. 108 is the longest valid AF_UNIX path for a binding. * sun_path[108] doesn't as such exist. However in kernel space * we are guaranteed that it is a valid memory location in our * kernel address buffer because syscall functions always pass * a pointer of struct sockaddr_storage which has a bigger buffer - * than 108. + * than 108. Also, we must terminate sun_path for strlen() in + * getname_kernel(). + */ + addr->__data[addr_len - offset] = 0; + + /* Don't pass sunaddr->sun_path to strlen(). Otherwise, 108 will + * cause panic if CONFIG_FORTIFY_SOURCE=y. Let __fortify_strlen() + * know the actual buffer. */ - ((char *)sunaddr)[addr_len] = 0; + return strlen(addr->__data) + offset + 1; } static void __unix_remove_socket(struct sock *sk) @@ -1208,8 +1220,7 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr, struct path parent; int err; - addr_len = strnlen(sunaddr->sun_path, sizeof(sunaddr->sun_path)) - + offsetof(struct sockaddr_un, sun_path) + 1; + addr_len = unix_mkname_bsd(sunaddr, addr_len); addr = unix_create_addr(sunaddr, addr_len); if (!addr) return -ENOMEM; -- cgit