diff options
author | David Howells <dhowells@redhat.com> | 2009-09-24 15:13:10 +0100 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-24 17:18:38 -0700 |
commit | 645d83c5db970a1c57225e155113b4aa2451e920 (patch) | |
tree | c86d3fb382e0ebabd8b96bb7883a8258c1cfe9d7 /mm/nommu.c | |
parent | c775197d59995228909957e9f0ec128de2590682 (diff) | |
download | lwn-645d83c5db970a1c57225e155113b4aa2451e920.tar.gz lwn-645d83c5db970a1c57225e155113b4aa2451e920.zip |
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.c | 34 |
1 files changed, 12 insertions, 22 deletions
diff --git a/mm/nommu.c b/mm/nommu.c index 56a446f05971..6a002abcb58f 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: |