[PATCH 28/38] union-mount: Implement union-aware access()/faccessat()
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From: Valerie Aurora on 6 Aug 2010 18:40 For union mounts, a file located on the lower layer will incorrectly return EROFS on an access check. To fix this, use the new path_permission() call, which ignores a read-only lower layer file system if the target will be copied up to the topmost file system. Signed-off-by: Valerie Aurora <vaurora(a)redhat.com> --- fs/open.c | 21 +++++++++++++++++---- 1 files changed, 17 insertions(+), 4 deletions(-) diff --git a/fs/open.c b/fs/open.c index 5463266..fc56da0 100644 --- a/fs/open.c +++ b/fs/open.c @@ -31,6 +31,7 @@ #include <linux/ima.h> #include "internal.h" +#include "union.h" int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs, struct file *filp) @@ -288,7 +289,10 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode) const struct cred *old_cred; struct cred *override_cred; struct path path; + struct nameidata nd; + struct vfsmount *mnt; struct inode *inode; + char *tmp; int res; if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */ @@ -312,10 +316,17 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode) old_cred = override_creds(override_cred); - res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path); + res = user_path_nd(dfd, filename, LOOKUP_FOLLOW, + &nd, &path, &tmp); if (res) goto out; + /* For union mounts, use the topmost mnt's permissions */ + if (IS_DIR_UNIONED(nd.path.dentry)) + mnt = nd.path.mnt; + else + mnt = path.mnt; + inode = path.dentry->d_inode; if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) { @@ -324,11 +335,11 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode) * with the "noexec" flag. */ res = -EACCES; - if (path.mnt->mnt_flags & MNT_NOEXEC) + if (mnt->mnt_flags & MNT_NOEXEC) goto out_path_release; } - res = inode_permission(inode, mode | MAY_ACCESS); + res = path_permission(&path, &nd.path, mode | MAY_ACCESS); /* SuS v2 requires we report a read only fs too */ if (res || !(mode & S_IWOTH) || special_file(inode->i_mode)) goto out_path_release; @@ -342,11 +353,13 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode) * inherently racy and know that the fs may change * state before we even see this result. */ - if (__mnt_is_readonly(path.mnt)) + if (__mnt_is_readonly(mnt)) res = -EROFS; out_path_release: path_put(&path); + path_put(&nd.path); + putname(tmp); out: revert_creds(old_cred); put_cred(override_cred); -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |