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authorDavid Howells <dhowells@redhat.com>2009-09-24 15:13:10 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-24 17:18:38 -0700
commit645d83c5db970a1c57225e155113b4aa2451e920 (patch)
treec86d3fb382e0ebabd8b96bb7883a8258c1cfe9d7 /mm/nommu.c
parentc775197d59995228909957e9f0ec128de2590682 (diff)
downloadvexpress-lsk-645d83c5db970a1c57225e155113b4aa2451e920.tar.gz
NOMMU: Fix MAP_PRIVATE mmap() of objects where the data can be mapped directly
Fix MAP_PRIVATE mmap() of files and devices where the data in the backing store might be mapped directly. Use the BDI_CAP_MAP_DIRECT capability flag to govern whether or not we should be trying to map a file directly. This can be used to determine whether or not a region has been filled in at the point where we call do_mmap_shared() or do_mmap_private(). The BDI_CAP_MAP_DIRECT capability flag is cleared by validate_mmap_request() if there's any reason we can't use it. It's also cleared in do_mmap_pgoff() if f_op->get_unmapped_area() fails. Without this fix, attempting to run a program from a RomFS image on a non-mappable MTD partition results in a BUG as the kernel attempts XIP, and this can be caught in gdb: Program received signal SIGABRT, Aborted. 0xc005dce8 in add_nommu_region (region=<value optimized out>) at mm/nommu.c:547 (gdb) bt #0 0xc005dce8 in add_nommu_region (region=<value optimized out>) at mm/nommu.c:547 #1 0xc005f168 in do_mmap_pgoff (file=0xc31a6620, addr=<value optimized out>, len=3808, prot=3, flags=6146, pgoff=0) at mm/nommu.c:1373 #2 0xc00a96b8 in elf_fdpic_map_file (params=0xc33fbbec, file=0xc31a6620, mm=0xc31bef60, what=0xc0213144 "executable") at mm.h:1145 #3 0xc00aa8b4 in load_elf_fdpic_binary (bprm=0xc316cb00, regs=<value optimized out>) at fs/binfmt_elf_fdpic.c:343 #4 0xc006b588 in search_binary_handler (bprm=0x6, regs=0xc33fbce0) at fs/exec.c:1234 #5 0xc006c648 in do_execve (filename=<value optimized out>, argv=0xc3ad14cc, envp=0xc3ad1460, regs=0xc33fbce0) at fs/exec.c:1356 #6 0xc0008cf0 in sys_execve (name=<value optimized out>, argv=0xc3ad14cc, envp=0xc3ad1460) at arch/frv/kernel/process.c:263 #7 0xc00075dc in __syscall_call () at arch/frv/kernel/entry.S:897 Note that this fix does the following commit differently: commit a190887b58c32d19c2eee007c5eb8faa970a69ba Author: David Howells <dhowells@redhat.com> Date: Sat Sep 5 11:17:07 2009 -0700 nommu: fix error handling in do_mmap_pgoff() Reported-by: Graff Yang <graff.yang@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Greg Ungerer <gerg@snapgear.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/nommu.c')
-rw-r--r--mm/nommu.c34
1 files changed, 12 insertions, 22 deletions
diff --git a/mm/nommu.c b/mm/nommu.c
index 56a446f0597..6a002abcb58 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1034,7 +1034,7 @@ static int do_mmap_shared_file(struct vm_area_struct *vma)
ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
if (ret == 0) {
vma->vm_region->vm_top = vma->vm_region->vm_end;
- return ret;
+ return 0;
}
if (ret != -ENOSYS)
return ret;
@@ -1051,7 +1051,8 @@ static int do_mmap_shared_file(struct vm_area_struct *vma)
*/
static int do_mmap_private(struct vm_area_struct *vma,
struct vm_region *region,
- unsigned long len)
+ unsigned long len,
+ unsigned long capabilities)
{
struct page *pages;
unsigned long total, point, n, rlen;
@@ -1062,13 +1063,13 @@ static int do_mmap_private(struct vm_area_struct *vma,
* shared mappings on devices or memory
* - VM_MAYSHARE will be set if it may attempt to share
*/
- if (vma->vm_file) {
+ if (capabilities & BDI_CAP_MAP_DIRECT) {
ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
if (ret == 0) {
/* shouldn't return success if we're not sharing */
BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
vma->vm_region->vm_top = vma->vm_region->vm_end;
- return ret;
+ return 0;
}
if (ret != -ENOSYS)
return ret;
@@ -1306,7 +1307,7 @@ unsigned long do_mmap_pgoff(struct file *file,
* - this is the hook for quasi-memory character devices to
* tell us the location of a shared mapping
*/
- if (file && file->f_op->get_unmapped_area) {
+ if (capabilities & BDI_CAP_MAP_DIRECT) {
addr = file->f_op->get_unmapped_area(file, addr, len,
pgoff, flags);
if (IS_ERR((void *) addr)) {
@@ -1330,15 +1331,17 @@ unsigned long do_mmap_pgoff(struct file *file,
}
vma->vm_region = region;
- add_nommu_region(region);
- /* set up the mapping */
+ /* set up the mapping
+ * - the region is filled in if BDI_CAP_MAP_DIRECT is still set
+ */
if (file && vma->vm_flags & VM_SHARED)
ret = do_mmap_shared_file(vma);
else
- ret = do_mmap_private(vma, region, len);
+ ret = do_mmap_private(vma, region, len, capabilities);
if (ret < 0)
- goto error_put_region;
+ goto error_just_free;
+ add_nommu_region(region);
/* okay... we have a mapping; now we have to register it */
result = vma->vm_start;
@@ -1356,19 +1359,6 @@ share:
kleave(" = %lx", result);
return result;
-error_put_region:
- __put_nommu_region(region);
- if (vma) {
- if (vma->vm_file) {
- fput(vma->vm_file);
- if (vma->vm_flags & VM_EXECUTABLE)
- removed_exe_file_vma(vma->vm_mm);
- }
- kmem_cache_free(vm_area_cachep, vma);
- }
- kleave(" = %d [pr]", ret);
- return ret;
-
error_just_free:
up_write(&nommu_region_sem);
error: