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authorMichael Ellerman <mpe@ellerman.id.au>2023-01-30 12:47:07 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2023-01-31 21:37:36 +1100
commit7294194b47e994753a86eee8cf1c61f3f36458a3 (patch)
tree5aca0a12aa6ed6790dde03ab033c78c260aae45b
parentad53db4acb415976761d7302f5b02e97f2bd097e (diff)
powerpc/kexec_file: Fix division by zero in extra size estimation
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> Link: https://lore.kernel.org/r/20230130014707.541110-1-mpe@ellerman.id.au
-rw-r--r--arch/powerpc/kexec/file_load_64.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index af8854f9eae3..19d084682bc2 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -989,10 +989,13 @@ 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