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Date: Wed, 22 Jun 2022 15:45:59 -0400 From: Gabriel Krisman Bertazi <krisman@...labora.com> To: viro@...iv.linux.org.uk, tytso@....edu, jaegeuk@...nel.org Cc: ebiggers@...nel.org, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, Gabriel Krisman Bertazi <krisman@...labora.com>, kernel@...labora.com Subject: [PATCH 3/7] libfs: Validate negative dentries in case-insensitive directories Introduce a dentry revalidation helper to be used by case-insensitive filesystems to check if it is safe to reuse a negative dentry. A negative dentry is safe to be reused on a case-insensitive lookup if it was created during a case-insensitive lookup and this is not a lookup that will instantiate a dentry. If this is a creation lookup, we also need to make sure the name matches sensitively the name under lookup in order to assure the name preserving semantics. Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com> --- fs/libfs.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/fs/libfs.c b/fs/libfs.c index 31b0ddf01c31..de43f3f585f1 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -1450,9 +1450,33 @@ static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str) return 0; } +static inline int generic_ci_d_revalidate(struct dentry *dentry, + const struct qstr *name, + unsigned int flags) +{ + int is_creation = flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET); + + if (d_is_negative(dentry)) { + const struct dentry *parent = READ_ONCE(dentry->d_parent); + const struct inode *dir = READ_ONCE(parent->d_inode); + + if (dir && needs_casefold(dir)) { + if (!d_is_casefold_lookup(dentry)) + return 0; + + if (is_creation && + (dentry->d_name.len != name->len || + memcmp(dentry->d_name.name, name->name, name->len))) + return 0; + } + } + return 1; +} + static const struct dentry_operations generic_ci_dentry_ops = { .d_hash = generic_ci_d_hash, .d_compare = generic_ci_d_compare, + .d_revalidate_name = generic_ci_d_revalidate, }; #endif -- 2.36.1
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