From: Eric Biggers <ebiggers@kernel.org> To: linux-f2fs-devel@lists.sourceforge.net Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>, Daniel Rosenberg <drosen@google.com>, Gabriel Krisman Bertazi <krisman@collabora.com> Subject: [PATCH 2/2] f2fs: fix race conditions in ->d_compare() and ->d_hash() Date: Thu, 23 Jan 2020 20:15:49 -0800 [thread overview] Message-ID: <20200124041549.159983-3-ebiggers@kernel.org> (raw) In-Reply-To: <20200124041549.159983-1-ebiggers@kernel.org> From: Eric Biggers <ebiggers@google.com> Since ->d_compare() and ->d_hash() can be called in RCU-walk mode, ->d_parent and ->d_inode can be concurrently modified, and in particular, ->d_inode may be changed to NULL. For f2fs_d_hash() this resulted in a reproducible NULL dereference if a lookup is done in a directory being deleted, e.g. with: int main() { if (fork()) { for (;;) { mkdir("subdir", 0700); rmdir("subdir"); } } else { for (;;) access("subdir/file", 0); } } ... or by running the 't_encrypted_d_revalidate' program from xfstests. Both repros work in any directory on a filesystem with the encoding feature, even if the directory doesn't actually have the casefold flag. I couldn't reproduce a crash in f2fs_d_compare(), but it appears that a similar crash is possible there. Fix these bugs by reading ->d_parent and ->d_inode using READ_ONCE() and falling back to the case sensitive behavior if the inode is NULL. Reported-by: Al Viro <viro@zeniv.linux.org.uk> Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups") Cc: <stable@vger.kernel.org> # v5.4+ Signed-off-by: Eric Biggers <ebiggers@google.com> --- fs/f2fs/dir.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index aea9e2806144d..d7c9a2cda4899 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1083,24 +1083,27 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name) { struct qstr qstr = {.name = str, .len = len }; + const struct dentry *parent = READ_ONCE(dentry->d_parent); + const struct inode *inode = READ_ONCE(parent->d_inode); - if (!IS_CASEFOLDED(dentry->d_parent->d_inode)) { + if (!inode || !IS_CASEFOLDED(inode)) { if (len != name->len) return -1; return memcmp(str, name->name, len); } - return f2fs_ci_compare(dentry->d_parent->d_inode, name, &qstr, false); + return f2fs_ci_compare(inode, name, &qstr, false); } static int f2fs_d_hash(const struct dentry *dentry, struct qstr *str) { struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb); const struct unicode_map *um = sbi->s_encoding; + const struct inode *inode = READ_ONCE(dentry->d_inode); unsigned char *norm; int len, ret = 0; - if (!IS_CASEFOLDED(dentry->d_inode)) + if (!inode || !IS_CASEFOLDED(inode)) return 0; norm = f2fs_kmalloc(sbi, PATH_MAX, GFP_ATOMIC); -- 2.25.0
WARNING: multiple messages have this Message-ID (diff)
From: Eric Biggers <ebiggers@kernel.org> To: linux-f2fs-devel@lists.sourceforge.net Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Gabriel Krisman Bertazi <krisman@collabora.com>, Alexander Viro <viro@zeniv.linux.org.uk>, Daniel Rosenberg <drosen@google.com> Subject: [f2fs-dev] [PATCH 2/2] f2fs: fix race conditions in ->d_compare() and ->d_hash() Date: Thu, 23 Jan 2020 20:15:49 -0800 [thread overview] Message-ID: <20200124041549.159983-3-ebiggers@kernel.org> (raw) In-Reply-To: <20200124041549.159983-1-ebiggers@kernel.org> From: Eric Biggers <ebiggers@google.com> Since ->d_compare() and ->d_hash() can be called in RCU-walk mode, ->d_parent and ->d_inode can be concurrently modified, and in particular, ->d_inode may be changed to NULL. For f2fs_d_hash() this resulted in a reproducible NULL dereference if a lookup is done in a directory being deleted, e.g. with: int main() { if (fork()) { for (;;) { mkdir("subdir", 0700); rmdir("subdir"); } } else { for (;;) access("subdir/file", 0); } } ... or by running the 't_encrypted_d_revalidate' program from xfstests. Both repros work in any directory on a filesystem with the encoding feature, even if the directory doesn't actually have the casefold flag. I couldn't reproduce a crash in f2fs_d_compare(), but it appears that a similar crash is possible there. Fix these bugs by reading ->d_parent and ->d_inode using READ_ONCE() and falling back to the case sensitive behavior if the inode is NULL. Reported-by: Al Viro <viro@zeniv.linux.org.uk> Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups") Cc: <stable@vger.kernel.org> # v5.4+ Signed-off-by: Eric Biggers <ebiggers@google.com> --- fs/f2fs/dir.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index aea9e2806144d..d7c9a2cda4899 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1083,24 +1083,27 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name) { struct qstr qstr = {.name = str, .len = len }; + const struct dentry *parent = READ_ONCE(dentry->d_parent); + const struct inode *inode = READ_ONCE(parent->d_inode); - if (!IS_CASEFOLDED(dentry->d_parent->d_inode)) { + if (!inode || !IS_CASEFOLDED(inode)) { if (len != name->len) return -1; return memcmp(str, name->name, len); } - return f2fs_ci_compare(dentry->d_parent->d_inode, name, &qstr, false); + return f2fs_ci_compare(inode, name, &qstr, false); } static int f2fs_d_hash(const struct dentry *dentry, struct qstr *str) { struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb); const struct unicode_map *um = sbi->s_encoding; + const struct inode *inode = READ_ONCE(dentry->d_inode); unsigned char *norm; int len, ret = 0; - if (!IS_CASEFOLDED(dentry->d_inode)) + if (!inode || !IS_CASEFOLDED(inode)) return 0; norm = f2fs_kmalloc(sbi, PATH_MAX, GFP_ATOMIC); -- 2.25.0 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
next prev parent reply other threads:[~2020-01-24 4:16 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-24 4:15 [PATCH 0/2] f2fs: fixes for f2fs_d_compare() and f2fs_d_hash() Eric Biggers 2020-01-24 4:15 ` [f2fs-dev] " Eric Biggers 2020-01-24 4:15 ` [PATCH 1/2] f2fs: fix dcache lookup of !casefolded directories Eric Biggers 2020-01-24 4:15 ` [f2fs-dev] " Eric Biggers 2020-01-24 4:15 ` Eric Biggers [this message] 2020-01-24 4:15 ` [f2fs-dev] [PATCH 2/2] f2fs: fix race conditions in ->d_compare() and ->d_hash() Eric Biggers
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