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ext4: fix deadlock between inline_data and ext4_expand_extra_isize_ea()
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commit c755e25 upstream.

The xattr_sem deadlock problems fixed in commit 2e81a4e: "ext4:
avoid deadlock when expanding inode size" didn't include the use of
xattr_sem in fs/ext4/inline.c.  With the addition of project quota
which added a new extra inode field, this exposed deadlocks in the
inline_data code similar to the ones fixed by 2e81a4e.

The deadlock can be reproduced via:

   dmesg -n 7
   mke2fs -t ext4 -O inline_data -Fq -I 256 /dev/vdc 32768
   mount -t ext4 -o debug_want_extra_isize=24 /dev/vdc /vdc
   mkdir /vdc/a
   umount /vdc
   mount -t ext4 /dev/vdc /vdc
   echo foo > /vdc/a/foo

and looks like this:

[   11.158815]
[   11.160276] =============================================
[   11.161960] [ INFO: possible recursive locking detected ]
[   11.161960] 4.10.0-rc3-00015-g011b30a8a3cf #160 Tainted: G        W
[   11.161960] ---------------------------------------------
[   11.161960] bash/2519 is trying to acquire lock:
[   11.161960]  (&ei->xattr_sem){++++..}, at: [<c1225a4b>] ext4_expand_extra_isize_ea+0x3d/0x4cd
[   11.161960]
[   11.161960] but task is already holding lock:
[   11.161960]  (&ei->xattr_sem){++++..}, at: [<c1227941>] ext4_try_add_inline_entry+0x3a/0x152
[   11.161960]
[   11.161960] other info that might help us debug this:
[   11.161960]  Possible unsafe locking scenario:
[   11.161960]
[   11.161960]        CPU0
[   11.161960]        ----
[   11.161960]   lock(&ei->xattr_sem);
[   11.161960]   lock(&ei->xattr_sem);
[   11.161960]
[   11.161960]  *** DEADLOCK ***
[   11.161960]
[   11.161960]  May be due to missing lock nesting notation
[   11.161960]
[   11.161960] 4 locks held by bash/2519:
[   11.161960]  #0:  (sb_writers#3){.+.+.+}, at: [<c11a2414>] mnt_want_write+0x1e/0x3e
[   11.161960]  #1:  (&type->i_mutex_dir_key){++++++}, at: [<c119508b>] path_openat+0x338/0x67a
[   11.161960]  #2:  (jbd2_handle){++++..}, at: [<c123314a>] start_this_handle+0x582/0x622
[   11.161960]  #3:  (&ei->xattr_sem){++++..}, at: [<c1227941>] ext4_try_add_inline_entry+0x3a/0x152
[   11.161960]
[   11.161960] stack backtrace:
[   11.161960] CPU: 0 PID: 2519 Comm: bash Tainted: G        W       4.10.0-rc3-00015-g011b30a8a3cf #160
[   11.161960] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1 04/01/2014
[   11.161960] Call Trace:
[   11.161960]  dump_stack+0x72/0xa3
[   11.161960]  __lock_acquire+0xb7c/0xcb9
[   11.161960]  ? kvm_clock_read+0x1f/0x29
[   11.161960]  ? __lock_is_held+0x36/0x66
[   11.161960]  ? __lock_is_held+0x36/0x66
[   11.161960]  lock_acquire+0x106/0x18a
[   11.161960]  ? ext4_expand_extra_isize_ea+0x3d/0x4cd
[   11.161960]  down_write+0x39/0x72
[   11.161960]  ? ext4_expand_extra_isize_ea+0x3d/0x4cd
[   11.161960]  ext4_expand_extra_isize_ea+0x3d/0x4cd
[   11.161960]  ? _raw_read_unlock+0x22/0x2c
[   11.161960]  ? jbd2_journal_extend+0x1e2/0x262
[   11.161960]  ? __ext4_journal_get_write_access+0x3d/0x60
[   11.161960]  ext4_mark_inode_dirty+0x17d/0x26d
[   11.161960]  ? ext4_add_dirent_to_inline.isra.12+0xa5/0xb2
[   11.161960]  ext4_add_dirent_to_inline.isra.12+0xa5/0xb2
[   11.161960]  ext4_try_add_inline_entry+0x69/0x152
[   11.161960]  ext4_add_entry+0xa3/0x848
[   11.161960]  ? __brelse+0x14/0x2f
[   11.161960]  ? _raw_spin_unlock_irqrestore+0x44/0x4f
[   11.161960]  ext4_add_nondir+0x17/0x5b
[   11.161960]  ext4_create+0xcf/0x133
[   11.161960]  ? ext4_mknod+0x12f/0x12f
[   11.161960]  lookup_open+0x39e/0x3fb
[   11.161960]  ? __wake_up+0x1a/0x40
[   11.161960]  ? lock_acquire+0x11e/0x18a
[   11.161960]  path_openat+0x35c/0x67a
[   11.161960]  ? sched_clock_cpu+0xd7/0xf2
[   11.161960]  do_filp_open+0x36/0x7c
[   11.161960]  ? _raw_spin_unlock+0x22/0x2c
[   11.161960]  ? __alloc_fd+0x169/0x173
[   11.161960]  do_sys_open+0x59/0xcc
[   11.161960]  SyS_open+0x1d/0x1f
[   11.161960]  do_int80_syscall_32+0x4f/0x61
[   11.161960]  entry_INT80_32+0x2f/0x2f
[   11.161960] EIP: 0xb76ad469
[   11.161960] EFLAGS: 00000286 CPU: 0
[   11.161960] EAX: ffffffda EBX: 08168ac8 ECX: 00008241 EDX: 000001b6
[   11.161960] ESI: b75e46bc EDI: b7755000 EBP: bfbdb108 ESP: bfbdafc0
[   11.161960]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b

Reported-by: George Spelvin <[email protected]>
Signed-off-by: Theodore Ts'o <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@tytso @gregkh
tytso authored and gregkh committed Mar 12, 2017
1 parent c4b6ff7 commit 7cf6b70
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Showing 3 changed files with 74 additions and 54 deletions.
66 changes: 30 additions & 36 deletions fs/ext4/inline.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -381,7 +381,7 @@ static int ext4_update_inline_data(handle_t *handle, struct inode *inode,
static int ext4_prepare_inline_data(handle_t *handle, struct inode *inode,
unsigned int len)
{
int ret, size;
int ret, size, no_expand;
struct ext4_inode_info *ei = EXT4_I(inode);

if (!ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA))
Expand All @@ -391,15 +391,14 @@ static int ext4_prepare_inline_data(handle_t *handle, struct inode *inode,
if (size < len)
return -ENOSPC;

down_write(&EXT4_I(inode)->xattr_sem);
ext4_write_lock_xattr(inode, &no_expand);

if (ei->i_inline_off)
ret = ext4_update_inline_data(handle, inode, len);
else
ret = ext4_create_inline_data(handle, inode, len);

up_write(&EXT4_I(inode)->xattr_sem);

ext4_write_unlock_xattr(inode, &no_expand);
return ret;
}

Expand Down Expand Up @@ -533,7 +532,7 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
struct inode *inode,
unsigned flags)
{
int ret, needed_blocks;
int ret, needed_blocks, no_expand;
handle_t *handle = NULL;
int retries = 0, sem_held = 0;
struct page *page = NULL;
Expand Down Expand Up @@ -573,7 +572,7 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
goto out;
}

down_write(&EXT4_I(inode)->xattr_sem);
ext4_write_lock_xattr(inode, &no_expand);
sem_held = 1;
/* If some one has already done this for us, just exit. */
if (!ext4_has_inline_data(inode)) {
Expand Down Expand Up @@ -610,7 +609,7 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
put_page(page);
page = NULL;
ext4_orphan_add(handle, inode);
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);
sem_held = 0;
ext4_journal_stop(handle);
handle = NULL;
Expand All @@ -636,7 +635,7 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
put_page(page);
}
if (sem_held)
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);
if (handle)
ext4_journal_stop(handle);
brelse(iloc.bh);
Expand Down Expand Up @@ -729,7 +728,7 @@ int ext4_try_to_write_inline_data(struct address_space *mapping,
int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len,
unsigned copied, struct page *page)
{
int ret;
int ret, no_expand;
void *kaddr;
struct ext4_iloc iloc;

Expand All @@ -747,7 +746,7 @@ int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len,
goto out;
}

down_write(&EXT4_I(inode)->xattr_sem);
ext4_write_lock_xattr(inode, &no_expand);
BUG_ON(!ext4_has_inline_data(inode));

kaddr = kmap_atomic(page);
Expand All @@ -757,7 +756,7 @@ int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len,
/* clear page dirty so that writepages wouldn't work for us. */
ClearPageDirty(page);

up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);
brelse(iloc.bh);
out:
return copied;
Expand All @@ -768,7 +767,7 @@ ext4_journalled_write_inline_data(struct inode *inode,
unsigned len,
struct page *page)
{
int ret;
int ret, no_expand;
void *kaddr;
struct ext4_iloc iloc;

Expand All @@ -778,11 +777,11 @@ ext4_journalled_write_inline_data(struct inode *inode,
return NULL;
}

down_write(&EXT4_I(inode)->xattr_sem);
ext4_write_lock_xattr(inode, &no_expand);
kaddr = kmap_atomic(page);
ext4_write_inline_data(inode, &iloc, kaddr, 0, len);
kunmap_atomic(kaddr);
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);

return iloc.bh;
}
Expand Down Expand Up @@ -1259,15 +1258,15 @@ static int ext4_convert_inline_data_nolock(handle_t *handle,
int ext4_try_add_inline_entry(handle_t *handle, struct ext4_filename *fname,
struct inode *dir, struct inode *inode)
{
int ret, inline_size;
int ret, inline_size, no_expand;
void *inline_start;
struct ext4_iloc iloc;

ret = ext4_get_inode_loc(dir, &iloc);
if (ret)
return ret;

down_write(&EXT4_I(dir)->xattr_sem);
ext4_write_lock_xattr(dir, &no_expand);
if (!ext4_has_inline_data(dir))
goto out;

Expand Down Expand Up @@ -1313,7 +1312,7 @@ int ext4_try_add_inline_entry(handle_t *handle, struct ext4_filename *fname,

out:
ext4_mark_inode_dirty(handle, dir);
up_write(&EXT4_I(dir)->xattr_sem);
ext4_write_unlock_xattr(dir, &no_expand);
brelse(iloc.bh);
return ret;
}
Expand Down Expand Up @@ -1673,15 +1672,15 @@ int ext4_delete_inline_entry(handle_t *handle,
struct buffer_head *bh,
int *has_inline_data)
{
int err, inline_size;
int err, inline_size, no_expand;
struct ext4_iloc iloc;
void *inline_start;

err = ext4_get_inode_loc(dir, &iloc);
if (err)
return err;

down_write(&EXT4_I(dir)->xattr_sem);
ext4_write_lock_xattr(dir, &no_expand);
if (!ext4_has_inline_data(dir)) {
*has_inline_data = 0;
goto out;
Expand Down Expand Up @@ -1715,7 +1714,7 @@ int ext4_delete_inline_entry(handle_t *handle,

ext4_show_inline_dir(dir, iloc.bh, inline_start, inline_size);
out:
up_write(&EXT4_I(dir)->xattr_sem);
ext4_write_unlock_xattr(dir, &no_expand);
brelse(iloc.bh);
if (err != -ENOENT)
ext4_std_error(dir->i_sb, err);
Expand Down Expand Up @@ -1814,11 +1813,11 @@ bool empty_inline_dir(struct inode *dir, int *has_inline_data)

int ext4_destroy_inline_data(handle_t *handle, struct inode *inode)
{
int ret;
int ret, no_expand;

down_write(&EXT4_I(inode)->xattr_sem);
ext4_write_lock_xattr(inode, &no_expand);
ret = ext4_destroy_inline_data_nolock(handle, inode);
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);

return ret;
}
Expand Down Expand Up @@ -1903,7 +1902,7 @@ int ext4_try_to_evict_inline_data(handle_t *handle,
void ext4_inline_data_truncate(struct inode *inode, int *has_inline)
{
handle_t *handle;
int inline_size, value_len, needed_blocks;
int inline_size, value_len, needed_blocks, no_expand;
size_t i_size;
void *value = NULL;
struct ext4_xattr_ibody_find is = {
Expand All @@ -1920,7 +1919,7 @@ void ext4_inline_data_truncate(struct inode *inode, int *has_inline)
if (IS_ERR(handle))
return;

down_write(&EXT4_I(inode)->xattr_sem);
ext4_write_lock_xattr(inode, &no_expand);
if (!ext4_has_inline_data(inode)) {
*has_inline = 0;
ext4_journal_stop(handle);
Expand Down Expand Up @@ -1978,7 +1977,7 @@ void ext4_inline_data_truncate(struct inode *inode, int *has_inline)
up_write(&EXT4_I(inode)->i_data_sem);
out:
brelse(is.iloc.bh);
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);
kfree(value);
if (inode->i_nlink)
ext4_orphan_del(handle, inode);
Expand All @@ -1994,7 +1993,7 @@ void ext4_inline_data_truncate(struct inode *inode, int *has_inline)

int ext4_convert_inline_data(struct inode *inode)
{
int error, needed_blocks;
int error, needed_blocks, no_expand;
handle_t *handle;
struct ext4_iloc iloc;

Expand All @@ -2016,15 +2015,10 @@ int ext4_convert_inline_data(struct inode *inode)
goto out_free;
}

down_write(&EXT4_I(inode)->xattr_sem);
if (!ext4_has_inline_data(inode)) {
up_write(&EXT4_I(inode)->xattr_sem);
goto out;
}

error = ext4_convert_inline_data_nolock(handle, inode, &iloc);
up_write(&EXT4_I(inode)->xattr_sem);
out:
ext4_write_lock_xattr(inode, &no_expand);
if (ext4_has_inline_data(inode))
error = ext4_convert_inline_data_nolock(handle, inode, &iloc);
ext4_write_unlock_xattr(inode, &no_expand);
ext4_journal_stop(handle);
out_free:
brelse(iloc.bh);
Expand Down
30 changes: 12 additions & 18 deletions fs/ext4/xattr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1188,16 +1188,14 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
struct ext4_xattr_block_find bs = {
.s = { .not_found = -ENODATA, },
};
unsigned long no_expand;
int no_expand;
int error;

if (!name)
return -EINVAL;
if (strlen(name) > 255)
return -ERANGE;
down_write(&EXT4_I(inode)->xattr_sem);
no_expand = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND);
ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
ext4_write_lock_xattr(inode, &no_expand);

error = ext4_reserve_inode_write(handle, inode, &is.iloc);
if (error)
Expand Down Expand Up @@ -1264,7 +1262,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
ext4_xattr_update_super_block(handle, inode->i_sb);
inode->i_ctime = current_time(inode);
if (!value)
ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
no_expand = 0;
error = ext4_mark_iloc_dirty(handle, inode, &is.iloc);
/*
* The bh is consumed by ext4_mark_iloc_dirty, even with
Expand All @@ -1278,9 +1276,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
cleanup:
brelse(is.iloc.bh);
brelse(bs.bh);
if (no_expand == 0)
ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);
return error;
}

Expand Down Expand Up @@ -1497,12 +1493,11 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
int error = 0, tried_min_extra_isize = 0;
int s_min_extra_isize = le16_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_min_extra_isize);
int isize_diff; /* How much do we need to grow i_extra_isize */
int no_expand;

if (ext4_write_trylock_xattr(inode, &no_expand) == 0)
return 0;

down_write(&EXT4_I(inode)->xattr_sem);
/*
* Set EXT4_STATE_NO_EXPAND to avoid recursion when marking inode dirty
*/
ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
retry:
isize_diff = new_extra_isize - EXT4_I(inode)->i_extra_isize;
if (EXT4_I(inode)->i_extra_isize >= new_extra_isize)
Expand Down Expand Up @@ -1584,17 +1579,16 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
EXT4_I(inode)->i_extra_isize = new_extra_isize;
brelse(bh);
out:
ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
up_write(&EXT4_I(inode)->xattr_sem);
ext4_write_unlock_xattr(inode, &no_expand);
return 0;

cleanup:
brelse(bh);
/*
* We deliberately leave EXT4_STATE_NO_EXPAND set here since inode
* size expansion failed.
* Inode size expansion failed; don't try again
*/
up_write(&EXT4_I(inode)->xattr_sem);
no_expand = 1;
ext4_write_unlock_xattr(inode, &no_expand);
return error;
}

Expand Down
32 changes: 32 additions & 0 deletions fs/ext4/xattr.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,38 @@ extern const struct xattr_handler ext4_xattr_security_handler;

#define EXT4_XATTR_NAME_ENCRYPTION_CONTEXT "c"

/*
* The EXT4_STATE_NO_EXPAND is overloaded and used for two purposes.
* The first is to signal that there the inline xattrs and data are
* taking up so much space that we might as well not keep trying to
* expand it. The second is that xattr_sem is taken for writing, so
* we shouldn't try to recurse into the inode expansion. For this
* second case, we need to make sure that we take save and restore the
* NO_EXPAND state flag appropriately.
*/
static inline void ext4_write_lock_xattr(struct inode *inode, int *save)
{
down_write(&EXT4_I(inode)->xattr_sem);
*save = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND);
ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
}

static inline int ext4_write_trylock_xattr(struct inode *inode, int *save)
{
if (down_write_trylock(&EXT4_I(inode)->xattr_sem) == 0)
return 0;
*save = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND);
ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
return 1;
}

static inline void ext4_write_unlock_xattr(struct inode *inode, int *save)
{
if (*save == 0)
ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
up_write(&EXT4_I(inode)->xattr_sem);
}

extern ssize_t ext4_listxattr(struct dentry *, char *, size_t);

extern int ext4_xattr_get(struct inode *, int, const char *, void *, size_t);
Expand Down

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