commit 0e410e158e5baa1300bdf678cea4f4e0cf9d8b94 upstream.
With KASAN enabled the kernel has two different memset() functions, one
with KASAN checks (memset) and one without (__memset). KASAN uses some
macro tricks to use the proper version where required. For example
memset() calls in mm/slub.c are without KASAN checks, since they operate
on poisoned slab object metadata.
The issue is that clang emits memset() calls even when there is no
memset() in the source code. They get linked with improper memset()
implementation and the kernel fails to boot due to a huge amount of KASAN
reports during early boot stages.
The solution is to add -fno-builtin flag for files with KASAN_SANITIZE :=
n marker.
Link: http://lkml.kernel.org/r/8ffecfffe04088c52c42b92739c2bd8a0bcb3f5e.1516384594.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ Nick : Backported to 4.4 avoiding KUBSAN ]
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Starting with gcc-8.1, we get a warning about all system call definitions,
which use an alias between functions with incompatible prototypes, e.g.:
In file included from ../mm/process_vm_access.c:19:
../include/linux/syscalls.h:211:18: warning: 'sys_process_vm_readv' alias between functions of incompatible types 'long int(pid_t, const struct iovec *, long unsigned int, const struct iovec *, long unsigned int, long unsigned int)' {aka 'long int(int, const struct iovec *, long unsigned int, const struct iovec *, long unsigned int, long unsigned int)'} and 'long int(long int, long int, long int, long int, long int, long int)' [-Wattribute-alias]
asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
^~~
../include/linux/syscalls.h:207:2: note: in expansion of macro '__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
../include/linux/syscalls.h:201:36: note: in expansion of macro 'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
^~~~~~~~~~~~~~~
../mm/process_vm_access.c:300:1: note: in expansion of macro 'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
^~~~~~~~~~~~~~~
../include/linux/syscalls.h:215:18: note: aliased declaration here
asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
^~~
../include/linux/syscalls.h:207:2: note: in expansion of macro '__SYSCALL_DEFINEx'
__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
^~~~~~~~~~~~~~~~~
../include/linux/syscalls.h:201:36: note: in expansion of macro 'SYSCALL_DEFINEx'
#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
^~~~~~~~~~~~~~~
../mm/process_vm_access.c:300:1: note: in expansion of macro 'SYSCALL_DEFINE6'
SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
This is really noisy and does not indicate a real problem. In the latest
mainline kernel, this was addressed by commit bee20031772a ("disable
-Wattribute-alias warning for SYSCALL_DEFINEx()"), which seems too invasive
to backport.
This takes a much simpler approach and just disables the warning across the
kernel.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 upstream.
Prasad reported that he has seen crashes in BPF subsystem with netd
on Android with arm64 in the form of (note, the taint is unrelated):
[ 4134.721483] Unable to handle kernel paging request at virtual address 800000001
[ 4134.820925] Mem abort info:
[ 4134.901283] Exception class = DABT (current EL), IL = 32 bits
[ 4135.016736] SET = 0, FnV = 0
[ 4135.119820] EA = 0, S1PTW = 0
[ 4135.201431] Data abort info:
[ 4135.301388] ISV = 0, ISS = 0x00000021
[ 4135.359599] CM = 0, WnR = 0
[ 4135.470873] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffe39b946000
[ 4135.499757] [0000000800000001] *pgd=0000000000000000, *pud=0000000000000000
[ 4135.660725] Internal error: Oops: 96000021 [#1] PREEMPT SMP
[ 4135.674610] Modules linked in:
[ 4135.682883] CPU: 5 PID: 1260 Comm: netd Tainted: G S W 4.14.19+ #1
[ 4135.716188] task: ffffffe39f4aa380 task.stack: ffffff801d4e0000
[ 4135.731599] PC is at bpf_prog_add+0x20/0x68
[ 4135.741746] LR is at bpf_prog_inc+0x20/0x2c
[ 4135.751788] pc : [<ffffff94ab7ad584>] lr : [<ffffff94ab7ad638>] pstate: 60400145
[ 4135.769062] sp : ffffff801d4e3ce0
[...]
[ 4136.258315] Process netd (pid: 1260, stack limit = 0xffffff801d4e0000)
[ 4136.273746] Call trace:
[...]
[ 4136.442494] 3ca0: ffffff94ab7ad584 0000000060400145 ffffffe3a01bf8f8 0000000000000006
[ 4136.460936] 3cc0: 0000008000000000 ffffff94ab844204 ffffff801d4e3cf0 ffffff94ab7ad584
[ 4136.479241] [<ffffff94ab7ad584>] bpf_prog_add+0x20/0x68
[ 4136.491767] [<ffffff94ab7ad638>] bpf_prog_inc+0x20/0x2c
[ 4136.504536] [<ffffff94ab7b5d08>] bpf_obj_get_user+0x204/0x22c
[ 4136.518746] [<ffffff94ab7ade68>] SyS_bpf+0x5a8/0x1a88
Android's netd was basically pinning the uid cookie BPF map in BPF
fs (/sys/fs/bpf/traffic_cookie_uid_map) and later on retrieving it
again resulting in above panic. Issue is that the map was wrongly
identified as a prog! Above kernel was compiled with clang 4.0,
and it turns out that clang decided to merge the bpf_prog_iops and
bpf_map_iops into a single memory location, such that the two i_ops
could then not be distinguished anymore.
Reason for this miscompilation is that clang has the more aggressive
-fmerge-all-constants enabled by default. In fact, clang source code
has a comment about it in lib/AST/ExprConstant.cpp on why it is okay
to do so:
Pointers with different bases cannot represent the same object.
(Note that clang defaults to -fmerge-all-constants, which can
lead to inconsistent results for comparisons involving the address
of a constant; this generally doesn't matter in practice.)
The issue never appeared with gcc however, since gcc does not enable
-fmerge-all-constants by default and even *explicitly* states in
it's option description that using this flag results in non-conforming
behavior, quote from man gcc:
Languages like C or C++ require each variable, including multiple
instances of the same variable in recursive calls, to have distinct
locations, so using this option results in non-conforming behavior.
There are also various clang bug reports open on that matter [1],
where clang developers acknowledge the non-conforming behavior,
and refer to disabling it with -fno-merge-all-constants. But even
if this gets fixed in clang today, there are already users out there
that triggered this. Thus, fix this issue by explicitly adding
-fno-merge-all-constants to the kernel's Makefile to generically
disable this optimization, since potentially other places in the
kernel could subtly break as well.
Note, there is also a flag called -fmerge-constants (not supported
by clang), which is more conservative and only applies to strings
and it's enabled in gcc's -O/-O2/-O3/-Os optimization levels. In
gcc's code, the two flags -fmerge-{all-,}constants share the same
variable internally, so when disabling it via -fno-merge-all-constants,
then we really don't merge any const data (e.g. strings), and text
size increases with gcc (14,927,214 -> 14,942,646 for vmlinux.o).
$ gcc -fverbose-asm -O2 foo.c -S -o foo.S
-> foo.S lists -fmerge-constants under options enabled
$ gcc -fverbose-asm -O2 -fno-merge-all-constants foo.c -S -o foo.S
-> foo.S doesn't list -fmerge-constants under options enabled
$ gcc -fverbose-asm -O2 -fno-merge-all-constants -fmerge-constants foo.c -S -o foo.S
-> foo.S lists -fmerge-constants under options enabled
Thus, as a workaround we need to set both -fno-merge-all-constants
*and* -fmerge-constants in the Makefile in order for text size to
stay as is.
[1] https://bugs.llvm.org/show_bug.cgi?id=18538
Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chenbo Feng <fengc@google.com>
Cc: Richard Smith <richard-llvm@metafoo.co.uk>
Cc: Chandler Carruth <chandlerc@gmail.com>
Cc: linux-kernel@vger.kernel.org
Tested-by: Prasad Sodagudi <psodagud@codeaurora.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
