Re: [PATCH v2] Fix display of Maximum Memory
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-01-16 05:53:55
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
Michael Bringmann [off-list ref] writes:
quoted hunk ↗ jump to hunk
Correct overflow problem in calculation+display of Maximum Memory value to syscfg where 32bits is insufficient. Signed-off-by: Michael Bringmann <redacted> --- arch/powerpc/platforms/pseries/lparcfg.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c index e33e8bc..f00411c 100644 --- a/arch/powerpc/platforms/pseries/lparcfg.c +++ b/arch/powerpc/platforms/pseries/lparcfg.c@@ -433,12 +433,12 @@ static void parse_em_data(struct seq_file *m) static void maxmem_data(struct seq_file *m) { - unsigned long maxmem = 0; + u64 maxmem = 0;
This is 64-bit only code, so u64 == unsigned long.
- maxmem += drmem_info->n_lmbs * drmem_info->lmb_size; - maxmem += hugetlb_total_pages() * PAGE_SIZE; + maxmem += (u64)drmem_info->n_lmbs * drmem_info->lmb_size;
The only problem AFAICS is n_lmbs is int and lmb_size is u32, so this multiplication will overflow.
+ maxmem += (u64)hugetlb_total_pages() * PAGE_SIZE;
hugetlb_total_pages() already returns unsigned long.
- seq_printf(m, "MaxMem=%ld\n", maxmem); + seq_printf(m, "MaxMem=%llu\n", maxmem); }
This should be sufficient?
diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
index e33e8bc4b69b..38c306551f76 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c@@ -435,10 +435,10 @@ static void maxmem_data(struct seq_file *m) { unsigned long maxmem = 0; - maxmem += drmem_info->n_lmbs * drmem_info->lmb_size; + maxmem += (unsigned long)drmem_info->n_lmbs * drmem_info->lmb_size; maxmem += hugetlb_total_pages() * PAGE_SIZE; - seq_printf(m, "MaxMem=%ld\n", maxmem); + seq_printf(m, "MaxMem=%lu\n", maxmem); } static int pseries_lparcfg_data(struct seq_file *m, void *v)
cheers