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authorHugh Dickins <hughd@google.com>2021-09-03 00:53:57 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-03 19:58:11 +0300
commit51cc3a6620a6ca934d468bda345678768493f5d8 (patch)
tree027998d57756dcca6c4c8717a0b8b29e499ca5c0 /fs/namei.c
parent9857a17f206ff374aea78bccfb687f145368be2e (diff)
downloadlinux-51cc3a6620a6ca934d468bda345678768493f5d8.tar.xz
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.c8
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;