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| author | Hugh Dickins <hughd@google.com> | 2021-09-02 23:53:57 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-03 18:58:11 +0200 |
| commit | 51cc3a6620a6ca934d468bda345678768493f5d8 (patch) | |
| tree | 027998d57756dcca6c4c8717a0b8b29e499ca5c0 /fs/namei.c | |
| parent | mm/gup: remove try_get_page(), call try_get_compound_head() directly (diff) | |
| download | linux-51cc3a6620a6ca934d468bda345678768493f5d8.tar.xz linux-51cc3a6620a6ca934d468bda345678768493f5d8.zip | |
fs, mm: fix race in unlinking swapfile
We had a recurring situation in which admin procedures setting up
swapfiles would race with test preparation clearing away swapfiles; and
just occasionally that got stuck on a swapfile "(deleted)" which could
never be swapped off. That is not supposed to be possible.
2.6.28 commit f9454548e17c ("don't unlink an active swapfile") admitted
that it was leaving a race window open: now close it.
may_delete() makes the IS_SWAPFILE check (amongst many others) before
inode_lock has been taken on target: now repeat just that simple check in
vfs_unlink() and vfs_rename(), after taking inode_lock.
Which goes most of the way to fixing the race, but swapon() must also
check after it acquires inode_lock, that the file just opened has not
already been unlinked.
Link: https://lkml.kernel.org/r/e17b91ad-a578-9a15-5e3-4989e0f999b5@google.com
Fixes: f9454548e17c ("don't unlink an active swapfile")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/namei.c b/fs/namei.c index bf6d8a738c59..ff866c07f4d2 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -4024,7 +4024,9 @@ int vfs_unlink(struct user_namespace *mnt_userns, struct inode *dir, return -EPERM; inode_lock(target); - if (is_local_mountpoint(dentry)) + if (IS_SWAPFILE(target)) + error = -EPERM; + else if (is_local_mountpoint(dentry)) error = -EBUSY; else { error = security_inode_unlink(dir, dentry); @@ -4526,6 +4528,10 @@ int vfs_rename(struct renamedata *rd) else if (target) inode_lock(target); + error = -EPERM; + if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target))) + goto out; + error = -EBUSY; if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) goto out; |