From: Michael Ellerman <mpe@ellerman.id.au>
To: <linuxppc-dev@lists.ozlabs.org>
Cc: sourabhjain@linux.ibm.com, hbathini@linux.ibm.com
Subject: [PATCH] powerpc/kexec_file: Fix division by zero in extra size estimation
Date: Mon, 30 Jan 2023 12:47:07 +1100 [thread overview]
Message-ID: <20230130014707.541110-1-mpe@ellerman.id.au> (raw)
In kexec_extra_fdt_size_ppc64() there's logic to estimate how much
extra space will be needed in the device tree for some memory related
properties.
That logic uses the size of RAM divided by drmem_lmb_size() to do the
estimation. However drmem_lmb_size() can be zero if the machine has no
hotpluggable memory configured, which is the case when booting with qemu
and no maxmem=x parameter is passed (the default).
The division by zero is reported by UBSAN, and can also lead to an
overflow and a warning from kvmalloc, and kdump kernel loading fails:
WARNING: CPU: 0 PID: 133 at mm/util.c:596 kvmalloc_node+0x15c/0x160
Modules linked in:
CPU: 0 PID: 133 Comm: kexec Not tainted 6.2.0-rc5-03455-g07358bd97810 #223
Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1200 0xf000005 of:SLOF,git-dd0dca pSeries
NIP: c00000000041ff4c LR: c00000000041fe58 CTR: 0000000000000000
REGS: c0000000096ef750 TRAP: 0700 Not tainted (6.2.0-rc5-03455-g07358bd97810)
MSR: 800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24248242 XER: 2004011e
CFAR: c00000000041fed0 IRQMASK: 0
...
NIP kvmalloc_node+0x15c/0x160
LR kvmalloc_node+0x68/0x160
Call Trace:
kvmalloc_node+0x68/0x160 (unreliable)
of_kexec_alloc_and_setup_fdt+0xb8/0x7d0
elf64_load+0x25c/0x4a0
kexec_image_load_default+0x58/0x80
sys_kexec_file_load+0x5c0/0x920
system_call_exception+0x128/0x330
system_call_vectored_common+0x15c/0x2ec
To fix it, skip the calculation if drmem_lmb_size() is zero.
Fixes: 2377c92e37fe ("powerpc/kexec_file: fix FDT size estimation for kdump kernel")
Cc: stable@vger.kernel.org # v5.12+
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/kexec/file_load_64.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index af8854f9eae3..3caee570e79b 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -989,10 +989,12 @@ unsigned int kexec_extra_fdt_size_ppc64(struct kimage *image)
* linux,drconf-usable-memory properties. Get an approximate on the
* number of usable memory entries and use for FDT size estimation.
*/
- usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) +
- (2 * (resource_size(&crashk_res) / drmem_lmb_size())));
-
- extra_size = (unsigned int)(usm_entries * sizeof(u64));
+ if (drmem_lmb_size()) {
+ usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) +
+ (2 * (resource_size(&crashk_res) / drmem_lmb_size())));
+ extra_size = (unsigned int)(usm_entries * sizeof(u64));
+ } else
+ extra_size = 0;
/*
* Get the number of CPU nodes in the current DT. This allows to
--
2.39.1
next reply other threads:[~2023-01-30 1:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-30 1:47 Michael Ellerman [this message]
2023-01-31 9:02 ` [PATCH] powerpc/kexec_file: Fix division by zero in extra size estimation Sourabh Jain
2023-02-01 1:55 ` Michael Ellerman
2023-02-01 4:23 ` Sourabh Jain
2023-02-02 7:00 ` Hari Bathini
2023-02-05 9:41 ` Michael Ellerman
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