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erofs: initialized fields can only be observed after bit is set 

commit ce063129181312f8781a047a50be439c5859747b upstream.

Currently, although set_bit() & test_bit() pairs are used as a fast-
path for initialized configurations. However, these atomic ops are
actually relaxed forms. Instead, load-acquire & store-release form is
needed to make sure uninitialized fields won't be observed in advance
here (yet no such corresponding bitops so use full barriers instead.)

Link: https://lore.kernel.org/r/20210209130618.15838-1-hsiangkao@aol.com
Fixes: 62dc45979f ("staging: erofs: fix race of initializing xattrs of a inode at the same time")
Fixes: 152a333a58 ("staging: erofs: add compacted compression indexes support")
Cc: <stable@vger.kernel.org> # 5.3+
Reported-by: Huang Jianan <huangjianan@oppo.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang 2021-02-09 21:06:18 +08:00 committed by Greg Kroah-Hartman
parent 4d09487509
commit 52f3bdb107
2 changed files with 18 additions and 2 deletions
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10
fs/erofs/xattr.c
View File

@ -48,8 +48,14 @@ static int init_inode_xattrs(struct inode *inode)
int ret = 0;
/* the most case is that xattrs of this inode are initialized. */
if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags))
if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) {
/*
* paired with smp_mb() at the end of the function to ensure
* fields will only be observed after the bit is set.
*/
smp_mb();
return 0;
}
if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_XATTR_BIT, TASK_KILLABLE))
return -ERESTARTSYS;
@ -137,6 +143,8 @@ static int init_inode_xattrs(struct inode *inode)
}
xattr_iter_end(&it, atomic_map);
/* paired with smp_mb() at the beginning of the function. */
smp_mb();
set_bit(EROFS_I_EA_INITED_BIT, &vi->flags);
out_unlock:

10
fs/erofs/zmap.c
View File

@ -36,8 +36,14 @@ static int fill_inode_lazy(struct inode *inode)
void *kaddr;
struct z_erofs_map_header *h;
if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags))
if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) {
/*
* paired with smp_mb() at the end of the function to ensure
* fields will only be observed after the bit is set.
*/
smp_mb();
return 0;
}
if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_Z_BIT, TASK_KILLABLE))
return -ERESTARTSYS;
@ -83,6 +89,8 @@ static int fill_inode_lazy(struct inode *inode)
vi->z_physical_clusterbits[1] = vi->z_logical_clusterbits +
((h->h_clusterbits >> 5) & 7);
/* paired with smp_mb() at the beginning of the function */
smp_mb();
set_bit(EROFS_I_Z_INITED_BIT, &vi->flags);
unmap_done:
kunmap_atomic(kaddr);