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checks: Introduce is_multiple_of()

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In a number of places we check if one number is a multiple of another,
using a modulus.  In some of those cases the divisor is potentially zero,
which needs special handling or we could trigger a divide by zero.

Introduce an is_multiple_of() helper to safely handle this case, and use
it in a bunch of places.  This should close Coverity issue 1501687, maybe
others as well.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2021-06-08 15:17:11 +10:00
parent e59ca36fb7
commit 4c2ef8f4d1
1 changed files with 13 additions and 5 deletions
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18
checks.c
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@ -143,6 +143,14 @@ static void check_nodes_props(struct check *c, struct dt_info *dti, struct node
check_nodes_props(c, dti, child);
}
static bool is_multiple_of(int multiple, int divisor)
{
if (divisor == 0)
return multiple == 0;
else
return (multiple % divisor) == 0;
}
static bool run_check(struct check *c, struct dt_info *dti)
{
struct node *dt = dti->dt;
@ -766,7 +774,7 @@ static void check_reg_format(struct check *c, struct dt_info *dti,
size_cells = node_size_cells(node->parent);
entrylen = (addr_cells + size_cells) * sizeof(cell_t);
if (!entrylen || (prop->val.len % entrylen) != 0)
if (!is_multiple_of(prop->val.len, entrylen))
FAIL_PROP(c, dti, node, prop, "property has invalid length (%d bytes) "
"(#address-cells == %d, #size-cells == %d)",
prop->val.len, addr_cells, size_cells);
@ -807,7 +815,7 @@ static void check_ranges_format(struct check *c, struct dt_info *dti,
"#size-cells (%d) differs from %s (%d)",
ranges, c_size_cells, node->parent->fullpath,
p_size_cells);
} else if ((prop->val.len % entrylen) != 0) {
} else if (!is_multiple_of(prop->val.len, entrylen)) {
FAIL_PROP(c, dti, node, prop, "\"%s\" property has invalid length (%d bytes) "
"(parent #address-cells == %d, child #address-cells == %d, "
"#size-cells == %d)", ranges, prop->val.len,
@ -1382,7 +1390,7 @@ static void check_property_phandle_args(struct check *c,
struct node *root = dti->dt;
int cell, cellsize = 0;
if (prop->val.len % sizeof(cell_t)) {
if (!is_multiple_of(prop->val.len, sizeof(cell_t))) {
FAIL_PROP(c, dti, node, prop,
"property size (%d) is invalid, expected multiple of %zu",
prop->val.len, sizeof(cell_t));
@ -1594,7 +1602,7 @@ static void check_interrupts_property(struct check *c,
if (!irq_prop)
return;
if (irq_prop->val.len % sizeof(cell_t))
if (!is_multiple_of(irq_prop->val.len, sizeof(cell_t)))
FAIL_PROP(c, dti, node, irq_prop, "size (%d) is invalid, expected multiple of %zu",
irq_prop->val.len, sizeof(cell_t));
@ -1643,7 +1651,7 @@ static void check_interrupts_property(struct check *c,
}
irq_cells = propval_cell(prop);
if (irq_prop->val.len % (irq_cells * sizeof(cell_t))) {
if (!is_multiple_of(irq_prop->val.len, irq_cells * sizeof(cell_t))) {
FAIL_PROP(c, dti, node, prop,
"size is (%d), expected multiple of %d",
irq_prop->val.len, (int)(irq_cells * sizeof(cell_t)));