Messages in this thread | | | Subject | Re: [PATCH 4.19,v2] VFS: Fix fuseblk memory leak caused by mount concurrency | From | "chenxiaosong (A)" <> | Date | Tue, 26 Oct 2021 10:18:11 +0800 |
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在 2021/10/20 20:30, Greg KH 写道: > On Wed, Oct 13, 2021 at 06:49:06PM +0800, chenxiaosong (A) wrote: >> 在 2021/10/13 18:38, chenxiaosong (A) 写道: >>> 在 2021/10/13 18:11, Greg KH 写道: >>>> On Wed, Oct 13, 2021 at 05:51:01PM +0800, ChenXiaoSong wrote: >>>>> If two processes mount same superblock, memory leak occurs: >>>>> >>>>> CPU0 | CPU1 >>>>> do_new_mount | do_new_mount >>>>> fs_set_subtype | fs_set_subtype >>>>> kstrdup | >>>>> | kstrdup >>>>> memrory leak | >>>>> >>>>> Fix this by adding a write lock while calling fs_set_subtype. >>>>> >>>>> Linus's tree already have refactoring patchset [1], one of them >>>>> can fix this bug: >>>>> c30da2e981a7 (fuse: convert to use the new mount API) >>>>> >>>>> Since we did not merge the refactoring patchset in this branch, >>>>> I create this patch. >>>>> >>>>> [1] https://patchwork.kernel.org/project/linux-fsdevel/patch/20190903113640.7984-3-mszeredi@redhat.com/ >>>>> >>>>> >>>>> Fixes: 79c0b2df79eb (add filesystem subtype support) >>>>> Cc: David Howells <dhowells@redhat.com> >>>>> Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com> >>>>> --- >>>>> v1: Can not mount sshfs ([PATCH linux-4.19.y] VFS: Fix fuseblk >>>>> memory leak caused by mount concurrency) >>>>> v2: Use write lock while writing superblock >>>>> >>>>> fs/namespace.c | 9 ++++++--- >>>>> 1 file changed, 6 insertions(+), 3 deletions(-) >>>> >>>> As you are referring to a fuse-only patch above, why are you trying to >>>> resolve this issue in the core namespace code instead? >>>> >>>> How does fuse have anything to do with this? >>>> >>>> confused, >>>> >>>> greg k-h >>>> . >>>> >>> >>> Now, only `fuse_fs_type` and `fuseblk_fs_type` has `FS_HAS_SUBTYPE` flag >>> in kernel code, but maybe there is a filesystem module(`struct >>> file_system_type` has `FS_HAS_SUBTYPE` flag). And only mounting fuseblk >>> filesystem(e.g. ntfs) will occur memory leak now. >> >> How about updating the subject as: VFS: Fix memory leak caused by mounting >> fs with subtype concurrency? > > That would be a better idea, but still, this is not obvious that this is > the correct fix at all... > . > Why is this patch not correct? Can you tell me more about it? Thanks.
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