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Subject[PATCH v2] x86: selective remapping in parse_setup_data()
Date
Type SETUP_PCI, added by setup_efi_pci(), may advertise a ROM size
larger than early_memremap() is able to handle, which is currently
limited to 256kB. If this occurs it leads to a NULL dereference in
parse_setup_data().

To avoid this, first remap the setup_data header, and remap the data
only for types actually parsed in parse_setup_data(). Type SETUP_PCI is
handled later by pcibios_add_device(), when ioremap() is available.

Signed-off-by: Linn Crosetto <linn@hp.com>
---
v2: add more detail to the explanation as requested by hpa
---
arch/x86/kernel/setup.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f8ec578..2063a49 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -423,6 +423,17 @@ static void __init reserve_initrd(void)
}
#endif /* CONFIG_BLK_DEV_INITRD */

+static void __init remap_setup_data(u64 pa_data, u32 data_len,
+ struct setup_data **data, u32 *map_len)
+{
+ if (data_len <= *map_len)
+ return;
+
+ early_iounmap(*data, *map_len);
+ *data = early_memremap(pa_data, data_len);
+ *map_len = data_len;
+}
+
static void __init parse_setup_data(void)
{
struct setup_data *data;
@@ -432,18 +443,16 @@ static void __init parse_setup_data(void)
while (pa_data) {
u32 data_len, map_len;

+ /* The data length may be too large for early remapping,
+ remap the data only when needed. */
map_len = max(PAGE_SIZE - (pa_data & ~PAGE_MASK),
(u64)sizeof(struct setup_data));
data = early_memremap(pa_data, map_len);
data_len = data->len + sizeof(struct setup_data);
- if (data_len > map_len) {
- early_iounmap(data, map_len);
- data = early_memremap(pa_data, data_len);
- map_len = data_len;
- }

switch (data->type) {
case SETUP_E820_EXT:
+ remap_setup_data(pa_data, data_len, &data, &map_len);
parse_e820_ext(data);
break;
case SETUP_DTB:
--
1.7.11.3


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