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dma-contiguous: fix truncation of numa_cma / cma_pernuma sizes >= 2G

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numa_cma=0:4G reserves nothing at all. dma_numa_cma_reserve() copies the
requested size into a local int before handing it to
cma_declare_contiguous_nid(), so 0x100000000 truncates to zero and the
loop skips the node silently. Both parameters are documented in
kernel-parameters.txt as nn[MG], so that is the syntax the documentation
invites.

Which bits survive decides what a request turns into: 4G, 8G and 16G
reserve nothing, 2G, 3G and 6G sign-extend into a size the allocator
rejects with a warning, and 5G quietly reserves 1G.

It reaches further than those parameters. On a CMA_SIZE_PERNUMA kernel
with no per-node parameter, dma_numa_cma_reserve() takes the per-node
size from the default area, so a plain cma=4G on a multi-node machine
feeds that size through the same local and loses every per-node area.

numa_cma_size[] and pernuma_size_bytes are both phys_addr_t, so use it
for the local too, and give early_numa_cma() separate variables for the
node id and the size while in there.

Fixes: d5cae2261b ("dma-contiguous: simplify numa cma area handling")
Cc: stable@vger.kernel.org
Assisted-by: Kiro:claude-opus-5
Signed-off-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Feng Tang <feng.tang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20260821224252.70640-1-graf@amazon.com
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Alexander Graf
2026-08-24 15:40:07 +02:00
committed by Marek Szyprowski
parent 121f9fd1c3
commit 1476cca098
1 changed files with 9 additions and 7 deletions
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kernel/dma/contiguous.c
+9 -7
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@@ -140,21 +140,22 @@ static bool numa_cma_configured __initdata;
static int __init early_numa_cma(char *p)
{
int nid, count = 0;
unsigned long tmp;
unsigned long node;
phys_addr_t size;
char *s = p;
while (*s) {
if (sscanf(s, "%lu%n", &tmp, &count) != 1)
if (sscanf(s, "%lu%n", &node, &count) != 1)
break;
if (s[count] == ':') {
if (tmp >= MAX_NUMNODES)
if (node >= MAX_NUMNODES)
break;
nid = array_index_nospec(tmp, MAX_NUMNODES);
nid = array_index_nospec(node, MAX_NUMNODES);
s += count + 1;
tmp = memparse(s, &s);
numa_cma_size[nid] = tmp;
size = memparse(s, &s);
numa_cma_size[nid] = size;
if (*s == ',')
s++;
@@ -207,9 +208,10 @@ static void __init dma_numa_cma_reserve(void)
pernuma_size_bytes = cma_get_size(dma_contiguous_default_area);
for_each_node(nid) {
int size, ret;
phys_addr_t size;
char name[CMA_MAX_NAME];
struct cma **cma;
int ret;
if (!node_online(nid)) {
if (pernuma_size_bytes || numa_cma_size[nid])