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https://gitlab.com/apparmor/apparmor.git
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59 lines
1.9 KiB
Diff
59 lines
1.9 KiB
Diff
From: Andreas Gruenbacher <agruen@suse.de>
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Subject: Make d_path() consistent across mount operations
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The path that __d_path() computes can become slightly inconsistent when it
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races with mount operations: it grabs the vfsmount_lock when traversing mount
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points, but immediately drops it again, only to re-grab it when it reaches the
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next mount point. The result is that the filename computed is not always
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consisent, and the file may never have had that name. (This is unlikely, but
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still possible.)
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Fix this by grabbing the vfsmount_lock when the first mount point is reached,
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and holding onto it until the d_cache lookup is completed.
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Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
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---
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fs/dcache.c | 14 ++++++++------
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1 file changed, 8 insertions(+), 6 deletions(-)
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--- a/fs/dcache.c
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+++ b/fs/dcache.c
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@@ -1783,7 +1783,7 @@ static char *__d_path(struct dentry *den
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struct dentry *root, struct vfsmount *rootmnt,
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char *buffer, int buflen, int fail_deleted)
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{
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- int namelen, is_slash;
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+ int namelen, is_slash, vfsmount_locked = 0;
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if (buflen < 2)
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return ERR_PTR(-ENAMETOOLONG);
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@@ -1806,14 +1806,14 @@ static char *__d_path(struct dentry *den
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struct dentry * parent;
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if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
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- spin_lock(&vfsmount_lock);
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- if (vfsmnt->mnt_parent == vfsmnt) {
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- spin_unlock(&vfsmount_lock);
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- goto global_root;
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+ if (!vfsmount_locked) {
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+ spin_lock(&vfsmount_lock);
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+ vfsmount_locked = 1;
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}
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+ if (vfsmnt->mnt_parent == vfsmnt)
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+ goto global_root;
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dentry = vfsmnt->mnt_mountpoint;
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vfsmnt = vfsmnt->mnt_parent;
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- spin_unlock(&vfsmount_lock);
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continue;
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}
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parent = dentry->d_parent;
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@@ -1832,6 +1832,8 @@ static char *__d_path(struct dentry *den
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*--buffer = '/';
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out:
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+ if (vfsmount_locked)
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+ spin_unlock(&vfsmount_lock);
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spin_unlock(&dcache_lock);
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return buffer;
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