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linux/net/unix
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Kuniyuki Iwashima ecb4534b6a af_unix: Terminate sun_path when bind()ing pathname socket. 
kernel test robot reported slab-out-of-bounds access in strlen(). [0]

Commit 06d4c8a808 ("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: 06d4c8a808 ("af_unix: Fix fortify_panic() in unix_bind_bsd().")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/netdev/202307262110.659e5e8-oliver.sang@intel.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230726190828.47874-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
History 2023-07-27 11:36:55 +02:00
..
af_unix.c af_unix: Terminate sun_path when bind()ing pathname socket. 2023-07-27 11:36:55 +02:00
diag.c af_unix: Get user_ns from in_skb in unix_diag_get_exact(). 2022-12-01 10:32:20 +01:00
garbage.c net: reclaim skb->scm_io_uring bit 2023-03-08 13:21:47 +00:00
Kconfig af_unix: Kconfig: make CONFIG_UNIX bool 2023-06-12 10:45:50 +01:00
Makefile af_unix: Implement ->psock_update_sk_prot() 2021-07-15 18:17:50 -07:00
scm.c net: reclaim skb->scm_io_uring bit 2023-03-08 13:21:47 +00:00
scm.h net: split out functions related to registering inflight socket files 2019-02-28 08:24:23 -07:00
sysctl_net_unix.c af_unix: fix unix_sysctl_register() error path 2022-07-09 12:27:33 +01:00
unix_bpf.c bpf, sockmap: Fix an infinite loop error when len is 0 in tcp_bpf_recvmsg_parser() 2023-03-03 17:25:15 +01:00