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| author | James Hogan <james.hogan@imgtec.com> | 2017-04-05 16:32:45 +0100 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2017-04-10 13:31:12 +0200 |
| commit | 9d7f29cdb4ca53506115cf1d7a02ce6013894df0 (patch) | |
| tree | 4e6c383138eae01654d1cfbd283f0208bd85df3a /arch/mips/kernel/cevt-r4k.c | |
| parent | f2b42866b1bb30c1f62a84f6d829b8789495da95 (diff) | |
| download | linux-9d7f29cdb4ca53506115cf1d7a02ce6013894df0.tar.bz2 | |
MIPS: cevt-r4k: Fix out-of-bounds array access
calculate_min_delta() may incorrectly access a 4th element of buf2[]
which only has 3 elements. This may trigger undefined behaviour and has
been reported to cause strange crashes in start_kernel() sometime after
timer initialization when built with GCC 5.3, possibly due to
register/stack corruption:
sched_clock: 32 bits at 200MHz, resolution 5ns, wraps every 10737418237ns
CPU 0 Unable to handle kernel paging request at virtual address ffffb0aa, epc == 8067daa8, ra == 8067da84
Oops[#1]:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.18 #51
task: 8065e3e0 task.stack: 80644000
$ 0 : 00000000 00000001 00000000 00000000
$ 4 : 8065b4d0 00000000 805d0000 00000010
$ 8 : 00000010 80321400 fffff000 812de408
$12 : 00000000 00000000 00000000 ffffffff
$16 : 00000002 ffffffff 80660000 806a666c
$20 : 806c0000 00000000 00000000 00000000
$24 : 00000000 00000010
$28 : 80644000 80645ed0 00000000 8067da84
Hi : 00000000
Lo : 00000000
epc : 8067daa8 start_kernel+0x33c/0x500
ra : 8067da84 start_kernel+0x318/0x500
Status: 11000402 KERNEL EXL
Cause : 4080040c (ExcCode 03)
BadVA : ffffb0aa
PrId : 0501992c (MIPS 1004Kc)
Modules linked in:
Process swapper/0 (pid: 0, threadinfo=80644000, task=8065e3e0, tls=00000000)
Call Trace:
[<8067daa8>] start_kernel+0x33c/0x500
Code: 24050240 0c0131f9 24849c64 <a200b0a8> 41606020 000000c0 0c1a45e6 00000000 0c1a5f44
UBSAN also detects the same issue:
================================================================
UBSAN: Undefined behaviour in arch/mips/kernel/cevt-r4k.c:85:41
load of address 80647e4c with insufficient space
for an object of type 'unsigned int'
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.18 #47
Call Trace:
[<80028f70>] show_stack+0x88/0xa4
[<80312654>] dump_stack+0x84/0xc0
[<8034163c>] ubsan_epilogue+0x14/0x50
[<803417d8>] __ubsan_handle_type_mismatch+0x160/0x168
[<8002dab0>] r4k_clockevent_init+0x544/0x764
[<80684d34>] time_init+0x18/0x90
[<8067fa5c>] start_kernel+0x2f0/0x500
=================================================================
buf2[] is intentionally only 3 elements so that the last element is the
median once 5 samples have been inserted, so explicitly prevent the
possibility of comparing against the 4th element rather than extending
the array.
Fixes: 1fa405552e33f2 ("MIPS: cevt-r4k: Dynamically calculate min_delta_ns")
Reported-by: Rabin Vincent <rabinv@axis.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Tested-by: Rabin Vincent <rabinv@axis.com>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.7.x-
Patchwork: https://patchwork.linux-mips.org/patch/15892/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel/cevt-r4k.c')
| -rw-r--r-- | arch/mips/kernel/cevt-r4k.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c index 804d2a2a19fe..dd6a18bc10ab 100644 --- a/arch/mips/kernel/cevt-r4k.c +++ b/arch/mips/kernel/cevt-r4k.c @@ -80,7 +80,7 @@ static unsigned int calculate_min_delta(void) } /* Sorted insert of 75th percentile into buf2 */ - for (k = 0; k < i; ++k) { + for (k = 0; k < i && k < ARRAY_SIZE(buf2); ++k) { if (buf1[ARRAY_SIZE(buf1) - 1] < buf2[k]) { l = min_t(unsigned int, i, ARRAY_SIZE(buf2) - 1); |