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SubjectRe: [PATCH v2] sparc: make copy_thread honor pid namespaces
On Sat, Feb 20, 2021 at 1:51 AM Dmitry V. Levin <ldv@altlinux.org> wrote:
>
> On sparc, fork and clone syscalls have an unusual semantics of
> returning the pid of the parent process to the child process.
>
> Apparently, the implementation did not honor pid namespaces at all,
> so the child used to get the pid of its parent in the init namespace.
>
> Fortunately, most users of these syscalls are not affected by this bug
> because they use another register to distinguish the parent process
> from its child, and the pid of the parent process is often discarded.
>
> Reproducer:

tested on my sparc64 ldom:

1. non-patched kernel (kernel 5.11.0-03615-g55f62bc87347), reproducer/test run:

$ gcc -Wall -O2 sparc-fork-namespace2.c
$ ./a.out
current: 72544, parent: 69045, fork returned: 72545
current: 72545, parent: 72544, fork returned: 72544
current: 72544, parent: 69045, fork returned: 72546
current: 1, parent: 0, fork returned: 72544

2. kernel patch applied, test run:

$ uname -a
Linux ttip 5.11.0-09279-g7c70f3a7488d-dirty #185 SMP Tue Feb 23
00:50:11 MSK 2021 sparc64 GNU/Linux

$ ./a.out
current: 939, parent: 918, fork returned: 940
current: 940, parent: 939, fork returned: 939
current: 939, parent: 918, fork returned: 941
a.out: wait: 0x9

and console/kernel logs:

[ 72.204212] Kernel unaligned access at TPC[4060c8] ret_from_fork+0x1c/0x2c
[ 72.204254] Unsupported unaligned load/store trap for kernel at
<00000000004060c8>.
[ 72.204267] \|/ ____ \|/
[ 72.204267] "@'/ .. \`@"
[ 72.204267] /_| \__/ |_\
[ 72.204267] \__U_/
[ 72.204284] a.out(941): Kernel does fpu/atomic unaligned load/store. [#3]
[ 72.204298] CPU: 6 PID: 941 Comm: a.out Tainted: G D E
5.11.0-09279-g7c70f3a7488d-dirty #185
[ 72.204315] TSTATE: 0000004411001600 TPC: 00000000004060c8 TNPC:
00000000004060cc Y: 000000cf Tainted: G D E
[ 72.204330] TPC: <ret_from_fork+0x1c/0x2c>
[ 72.204340] g0: 0000000000000000 g1: ffffffffffffffff g2:
0000000000000006 g3: 0000000000000000
[ 72.204349] g4: fff8000041482700 g5: fff80021a9890000 g6:
fff8000041038000 g7: 0308000108000004
[ 72.204359] o0: 0000000000000000 o1: 000000001fffffff o2:
fff8000041482780 o3: 0000000000000000
[ 72.204369] o4: 0000000000000001 o5: 0000000000000000 sp:
fff800004103b6a1 ret_pc: 00000000004060b0
[ 72.204378] RPC: <ret_from_fork+0x4/0x2c>
[ 72.204387] l0: 0308000108000000 l1: 0000000000000002 l2:
0000000000450cf4 l3: 0000000000000000
[ 72.204396] l4: 0000000000000264 l5: 00000100001eb9f0 l6:
fff8000045018000 l7: 00000000006c7840
[ 72.204406] i0: 0000000000efcd60 i1: 0000000000450df4 i2:
00000000000003dc i3: 00000000000003dc
[ 72.204415] i4: 0000000000eebc78 i5: 0000000000000000 i6:
000007feffa56811 i7: 0000010000000ad8
[ 72.204424] I7: <0x10000000ad8>
[ 72.204432] Call Trace:
[ 72.204439] Caller[0000010000000ad8]: 0x10000000ad8
[ 72.204446] Instruction DUMP:
[ 72.204449] 0aca0072
[ 72.204456] e059a008
[ 72.204461] e25ba8c7
[ 72.204467] <9fc44000>
[ 72.204472] d05ba8cf
[ 72.204477] 1068006d
[ 72.204483] 90102000
[ 72.204488] 0f0011a9
[ 72.204493] 10680004
[ 72.204499]


So something is actually wrong with the patch.

Thanks.

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