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autofs4: fix indirect mount pending expire race

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The selection of a dentry for expiration and the setting of the
AUTOFS_INF_EXPIRING flag isn't done atomically which can lead to lookups
walking into an expiring mount.

What happens is that an expire is initiated by the daemon and a dentry is
selected for expire but, since there is no lock held between the selection
and setting of the expiring flag, a process may find the flag clear and
continue walking into the mount tree at the same time the daemon attempts
the expire it.

Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ian Kent
2008-07-23 21:30:26 -07:00
committed by Linus Torvalds
parent 26e81b3142
commit 97e7449a7a
3 changed files with 65 additions and 23 deletions
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10
fs/autofs4/autofs_i.h
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@@ -138,18 +138,14 @@ static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
static inline int autofs4_ispending(struct dentry *dentry)
{
struct autofs_info *inf = autofs4_dentry_ino(dentry);
int pending = 0;
if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
return 1;
if (inf) {
spin_lock(&inf->sbi->fs_lock);
pending = inf->flags & AUTOFS_INF_EXPIRING;
spin_unlock(&inf->sbi->fs_lock);
}
if (inf->flags & AUTOFS_INF_EXPIRING)
return 1;
return pending;
return 0;
}
static inline void autofs4_copy_atime(struct file *src, struct file *dst)