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From: Mike Frysinger on 9 Mar 2010 11:20
From: Bernd Schmidt <bernds_cb1(a)t-online.de>

Slightly rearrange the logic that determines capabilities and vm_flags.
Disable BDI_CAP_MAP_DIRECT in all cases if the device can't support the
protections. Allow private readonly mappings of readonly backing devices.

Signed-off-by: Bernd Schmidt <bernds_cb1(a)t-online.de>
Signed-off-by: Mike Frysinger <vapier(a)gentoo.org>
---
mm/nommu.c | 32 ++++++++++++++++++--------------
1 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 61a68d5..5767237 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -930,14 +930,6 @@ static int validate_mmap_request(struct file *file,
if (!(capabilities & BDI_CAP_MAP_DIRECT))
return -ENODEV;

- if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) ||
- ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
- ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP))
- ) {
- printk("MAP_SHARED not completely supported on !MMU\n");
- return -EINVAL;
- }
-
/* we mustn't privatise shared mappings */
capabilities &= ~BDI_CAP_MAP_COPY;
}
@@ -953,6 +945,20 @@ static int validate_mmap_request(struct file *file,
capabilities &= ~BDI_CAP_MAP_DIRECT;
}

+ if (capabilities & BDI_CAP_MAP_DIRECT) {
+ if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) ||
+ ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
+ ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP))
+ ) {
+ capabilities &= ~BDI_CAP_MAP_DIRECT;
+ if (flags & MAP_SHARED) {
+ printk(KERN_WARNING
+ "MAP_SHARED not completely supported on !MMU\n");
+ return -EINVAL;
+ }
+ }
+ }
+
/* handle executable mappings and implied executable
* mappings */
if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
@@ -1008,22 +1014,20 @@ static unsigned long determine_vm_flags(struct file *file,
unsigned long vm_flags;

vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
- vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
/* vm_flags |= mm->def_flags; */

if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
/* attempt to share read-only copies of mapped file chunks */
+ vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
if (file && !(prot & PROT_WRITE))
vm_flags |= VM_MAYSHARE;
- }
- else {
+ } else {
/* overlay a shareable mapping on the backing device or inode
* if possible - used for chardevs, ramfs/tmpfs/shmfs and
* romfs/cramfs */
+ vm_flags |= VM_MAYSHARE | (capabilities & BDI_CAP_VMFLAGS);
if (flags & MAP_SHARED)
- vm_flags |= VM_MAYSHARE | VM_SHARED;
- else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
- vm_flags |= VM_MAYSHARE;
+ vm_flags |= VM_SHARED;
}

/* refuse to let anyone share private mappings with this process if
--
1.7.0.2

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Prev: How to tell we're using the KMS (during suspend/resume) outside the graphics driver
Next: CONFIG_I2C_XILINX doesn't complie