The patch titled
sysfs: fix deadlock
has been added to the -mm tree. Its filename is
sysfs-fix-deadlock.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: sysfs: fix deadlock
From: Nick Piggin <npiggin@xxxxxxx>
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.27-rc6-tip #1
-------------------------------------------------------
X/4873 is trying to acquire lock:
(&bb->mutex){--..}, at: [<c020ba20>] mmap+0x40/0xa0
but task is already holding lock:
(&mm->mmap_sem){----}, at: [<c0125a1e>] sys_mmap2+0x8e/0xc0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mm->mmap_sem){----}:
[<c017dc96>] validate_chain+0xa96/0xf50
[<c017ef2b>] __lock_acquire+0x2cb/0x5b0
[<c017f299>] lock_acquire+0x89/0xc0
[<c01aa8fb>] might_fault+0x6b/0x90
[<c040b618>] copy_to_user+0x38/0x60
[<c020bcfb>] read+0xfb/0x170
[<c01c09a5>] vfs_read+0x95/0x110
[<c01c1443>] sys_pread64+0x63/0x80
[<c012146f>] sysenter_do_call+0x12/0x43
[<ffffffff>] 0xffffffff
-> #0 (&bb->mutex){--..}:
[<c017d8b7>] validate_chain+0x6b7/0xf50
[<c017ef2b>] __lock_acquire+0x2cb/0x5b0
[<c017f299>] lock_acquire+0x89/0xc0
[<c0d6f2ab>] __mutex_lock_common+0xab/0x3c0
[<c0d6f698>] mutex_lock_nested+0x38/0x50
[<c020ba20>] mmap+0x40/0xa0
[<c01b111e>] mmap_region+0x14e/0x450
[<c01b170f>] do_mmap_pgoff+0x2ef/0x310
[<c0125a3d>] sys_mmap2+0xad/0xc0
[<c012146f>] sysenter_do_call+0x12/0x43
[<ffffffff>] 0xffffffff
other info that might help us debug this:
1 lock held by X/4873:
#0: (&mm->mmap_sem){----}, at: [<c0125a1e>] sys_mmap2+0x8e/0xc0
stack backtrace:
Pid: 4873, comm: X Not tainted 2.6.27-rc6-tip #1
[<c017cd09>] print_circular_bug_tail+0x79/0xc0
[<c017d8b7>] validate_chain+0x6b7/0xf50
[<c017a5b5>] ? trace_hardirqs_off_caller+0x15/0xb0
[<c017ef2b>] __lock_acquire+0x2cb/0x5b0
[<c017f299>] lock_acquire+0x89/0xc0
[<c020ba20>] ? mmap+0x40/0xa0
[<c0d6f2ab>] __mutex_lock_common+0xab/0x3c0
[<c020ba20>] ? mmap+0x40/0xa0
[<c0d6f698>] mutex_lock_nested+0x38/0x50
[<c020ba20>] ? mmap+0x40/0xa0
[<c020ba20>] mmap+0x40/0xa0
[<c01b111e>] mmap_region+0x14e/0x450
[<c01afb88>] ? arch_get_unmapped_area_topdown+0xf8/0x160
[<c01b170f>] do_mmap_pgoff+0x2ef/0x310
[<c0125a3d>] sys_mmap2+0xad/0xc0
[<c012146f>] sysenter_do_call+0x12/0x43
[<c0120000>] ? __switch_to+0x130/0x220
=======================
evbug.c: Event. Dev: input3, Type: 20, Code: 0, Value: 500
warning: `sudo' uses deprecated v2 capabilities in a way that may be insecure.
bin.c takes bb->mutex under mmap_sem when it is mmapped, and then does its
copy_*_user under bb->mutex too.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Reported-by: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/sysfs/bin.c | 42 +++++++++++++++++++++++++++++++-----------
1 file changed, 31 insertions(+), 11 deletions(-)
diff -puN fs/sysfs/bin.c~sysfs-fix-deadlock fs/sysfs/bin.c
--- a/fs/sysfs/bin.c~sysfs-fix-deadlock
+++ a/fs/sysfs/bin.c
@@ -61,6 +61,7 @@ read(struct file *file, char __user *use
int size = dentry->d_inode->i_size;
loff_t offs = *off;
int count = min_t(size_t, bytes, PAGE_SIZE);
+ char *temp;
if (size) {
if (offs > size)
@@ -69,23 +70,33 @@ read(struct file *file, char __user *use
count = size - offs;
}
+ temp = kmalloc(count, GFP_KERNEL);
+ if (!temp)
+ return -ENOMEM;
+
mutex_lock(&bb->mutex);
count = fill_read(dentry, bb->buffer, offs, count);
- if (count < 0)
- goto out_unlock;
+ if (count < 0) {
+ mutex_unlock(&bb->mutex);
+ goto out_free;
+ }
- if (copy_to_user(userbuf, bb->buffer, count)) {
+ memcpy(temp, bb->buffer, count);
+
+ mutex_unlock(&bb->mutex);
+
+ if (copy_to_user(userbuf, temp, count)) {
count = -EFAULT;
- goto out_unlock;
+ goto out_free;
}
pr_debug("offs = %lld, *off = %lld, count = %d\n", offs, *off, count);
*off = offs + count;
- out_unlock:
- mutex_unlock(&bb->mutex);
+ out_free:
+ kfree(temp);
return count;
}
@@ -118,6 +129,7 @@ static ssize_t write(struct file *file,
int size = dentry->d_inode->i_size;
loff_t offs = *off;
int count = min_t(size_t, bytes, PAGE_SIZE);
+ char *temp;
if (size) {
if (offs > size)
@@ -126,19 +138,27 @@ static ssize_t write(struct file *file,
count = size - offs;
}
- mutex_lock(&bb->mutex);
+ temp = kmalloc(count, GFP_KERNEL);
+ if (!temp)
+ return -ENOMEM;
- if (copy_from_user(bb->buffer, userbuf, count)) {
+ if (copy_from_user(temp, userbuf, count)) {
count = -EFAULT;
- goto out_unlock;
+ goto out_free;
}
+ mutex_lock(&bb->mutex);
+
+ memcpy(bb->buffer, temp, count);
+
count = flush_write(dentry, bb->buffer, offs, count);
+ mutex_unlock(&bb->mutex);
+
if (count > 0)
*off = offs + count;
- out_unlock:
- mutex_unlock(&bb->mutex);
+out_free:
+ kfree(temp);
return count;
}
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
linux-next.patch
sysfs-fix-deadlock.patch
inotify-fix-lock-ordering-wrt-do_page_faults-mmap_sem.patch
mm-tiny-shmem-fix-lor-mmap_sem-vs-i_mutex.patch
mm-tiny-shmem-fix-lor-mmap_sem-vs-i_mutex-checkpatch-fixes.patch
vmscan-move-isolate_lru_page-to-vmscanc.patch
mlock-mlocked-pages-are-unevictable.patch
mlock-mlocked-pages-are-unevictable-fix.patch
mmap-handle-mlocked-pages-during-map-remap-unmap.patch
vmstat-mlocked-pages-statistics.patch
mm-pagecache-insertion-fewer-atomics.patch
mm-unlockless-reclaim.patch
mm-page-lock-use-lock-bitops.patch
fs-buffer-lock-use-lock-bitops.patch
mm-page-allocator-minor-speedup.patch
mm-rewrite-vmap-layer.patch
mm-rewrite-vmap-layer-fix.patch
mm-rewrite-vmap-layer-fix-fix.patch
mm-rewrite-vmap-layer-fix-fix-fix.patch
reiser4.patch
likeliness-accounting-change-and-cleanup.patch
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