(2013/10/17 16:23), Jan Beulich wrote:
On 16.10.13 at 22:40, Andrew Morton <a...@linux-foundation.org> wrote:
On Wed, 16 Oct 2013 12:32:40 +0100 "Jan Beulich" <jbeul...@suse.com> wrote:
Commit c4fe24485729fc2cbff324c111e67a1cc2f9adea ("sparc: fix PCI device
proc file mmap(2)"), while fixing one problem, introduced two new ones:
- the function truncates the return value from ->get_unmapped_area() on
64-bit architectures,
- _all_ descendants are now required to set .get_unmapped_area to non-
NULL, which wasn't necessary before (and shouldn't be).
Both - afaict - are a result from a too simplistic copy'n'paste from
proc_reg_mmap() done in that change.
This likely also addresses reports like the one at
http://linux-kernel.2935.n7.nabble.com/mmap-for-proc-vmcore-broken-since-3-12-rc1-td729
326.html.
...
--- 3.12-rc5/fs/proc/inode.c
+++ 3.12-rc5-proc-get-unmapped-area/fs/proc/inode.c
@@ -288,12 +288,12 @@ static int proc_reg_mmap(struct file *fi
static unsigned long proc_reg_get_unmapped_area(struct file *file, unsigned
long orig_addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
struct proc_dir_entry *pde = PDE(file_inode(file));
- int rv = -EIO;
- unsigned long (*get_unmapped_area)(struct file *, unsigned long,
unsigned
long, unsigned long, unsigned long);
+ unsigned long rv = -EIO;
+
if (use_pde(pde)) {
- get_unmapped_area = pde->proc_fops->get_unmapped_area;
- if (get_unmapped_area)
- rv = get_unmapped_area(file, orig_addr, len, pgoff,
flags);
+ rv = (pde->proc_fops->get_unmapped_area
+ ?: current->mm->get_unmapped_area)(file, orig_addr, len,
+ pgoff, flags);
unuse_pde(pde);
}
return rv;
I think these two patches will address the problems:
http://ozlabs.org/~akpm/mmots/broken-out/procfs-fix-unintended-truncation-of-retur
ned-mapped-address.patch
http://ozlabs.org/~akpm/mmots/broken-out/procfs-call-default-get_unmapped_area-on-
mmu-present-architectures.patch
I'll be sending those Linuswards today. Please check them. (I think
your version would break the nommu build).
Yes indeed - I did search for existing patches, but didn't find them.
I see Linus merged them already, so there's no point anymore
sending Reviewed-by tags.
I think though that in the !MMU case the second of them leaves an
issue unfixed nevertheless: If the specific procfs handler has no
.get_unmapped_area, the operation would still fail in that case
rather than succeed as it did before that wrapper got added.)
Jan
Yes, there remains difference on no-mmu that if mmap is not defined, mmap() now
returns
EIO, it should return ENODEV.
In mm/nommu.c,
/* eliminate any capabilities that we can't support on this
* device */
if (!file->f_op->get_unmapped_area)
capabilities &= ~BDI_CAP_MAP_DIRECT;
and
*/
if (capabilities & BDI_CAP_MAP_DIRECT) {
addr = file->f_op->get_unmapped_area(file, addr, len,
pgoff, flags);
if (IS_ERR_VALUE(addr)) {
ret = addr;
if (ret != -ENOSYS)
goto error_just_free;
/* the driver refused to tell us where to site
* the mapping so we'll have to attempt to copy
* it */
ret = -ENODEV;
if (!(capabilities & BDI_CAP_MAP_COPY))
goto error_just_free;
capabilities &= ~BDI_CAP_MAP_DIRECT;
} else {
vma->vm_start = region->vm_start = addr;
vma->vm_end = region->vm_end = addr + len;
}
}
So, how about let proc_reg_get_unmapped_area() return ENOSYS, not EIO?
--
Thanks.
HATAYAMA, Daisuke
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