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Wed, 01 Jul 2026 15:02:16 -0700 (PDT) From: =?UTF-8?q?=EC=9D=B4=EC=83=81=ED=98=B8?= To: Bob Copeland Cc: linux-karma-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, =?UTF-8?q?=EC=9D=B4=EC=83=81=ED=98=B8?= Subject: [PATCH 1/2] omfs: detect directory sibling chain cycles Date: Thu, 2 Jul 2026 07:02:10 +0900 Message-ID: <20260701220211.822033-2-kudo3228@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260701220211.822033-1-kudo3228@gmail.com> References: <20260701220211.822033-1-kudo3228@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit OMFS directory lookup follows an on-disk sibling chain until it reaches the ~0 terminator. The sibling block number is image-controlled, so a crafted image can point an entry back to itself or create a small cycle. Lookup of a missing name in that hash bucket then spins in the kernel. Detect cycles in OMFS directory sibling chains and return -ELOOP from lookup when a cycle is found. Readdir uses the same detection to stop traversing malformed chains. Fixes: a3ab7155ea21 ("omfs: add directory routines") Signed-off-by: 이상호 --- fs/omfs/dir.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/fs/omfs/dir.c b/fs/omfs/dir.c index 2ed541fccf33..11b680f1c383 100644 --- a/fs/omfs/dir.c +++ b/fs/omfs/dir.c @@ -31,6 +31,56 @@ static struct buffer_head *omfs_get_bucket(struct inode *dir, return omfs_bread(dir->i_sb, dir->i_ino); } +static int omfs_get_sibling(struct inode *dir, u64 block, u64 *sibling) +{ + struct buffer_head *bh; + struct omfs_inode *oi; + + bh = omfs_bread(dir->i_sb, block); + if (!bh) + return -EIO; + + oi = (struct omfs_inode *)bh->b_data; + if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, block)) { + brelse(bh); + return -EIO; + } + + *sibling = be64_to_cpu(oi->i_sibling); + brelse(bh); + return 0; +} + +static int omfs_check_chain_cycle(struct inode *dir, u64 *slow, u64 *fast) +{ + int err; + + if (*fast == ~0) + return 0; + + err = omfs_get_sibling(dir, *fast, fast); + if (err) + return err; + + if (*fast == ~0) + return 0; + + err = omfs_get_sibling(dir, *fast, fast); + if (err) + return err; + + if (*slow != ~0) { + err = omfs_get_sibling(dir, *slow, slow); + if (err) + return err; + } + + if (*slow != ~0 && *slow == *fast) + return -ELOOP; + + return 0; +} + static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block, const char *name, int namelen, u64 *prev_block) @@ -38,6 +88,8 @@ static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block, struct buffer_head *bh; struct omfs_inode *oi; int err = -ENOENT; + u64 slow = block; + u64 fast = block; *prev_block = ~0; while (block != ~0) { @@ -59,6 +111,10 @@ static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block, *prev_block = block; block = be64_to_cpu(oi->i_sibling); brelse(bh); + + err = omfs_check_chain_cycle(dir, &slow, &fast); + if (err) + goto err; } err: return ERR_PTR(err); @@ -331,12 +387,15 @@ static bool omfs_fill_chain(struct inode *dir, struct dir_context *ctx, u64 fsblock, int hindex) { /* follow chain in this bucket */ + u64 slow = fsblock; + u64 fast = fsblock; while (fsblock != ~0) { - struct buffer_head *bh = omfs_bread(dir->i_sb, fsblock); + struct buffer_head *bh; struct omfs_inode *oi; u64 self; unsigned char d_type; + bh = omfs_bread(dir->i_sb, fsblock); if (!bh) return true; @@ -366,6 +425,9 @@ static bool omfs_fill_chain(struct inode *dir, struct dir_context *ctx, } brelse(bh); ctx->pos++; + + if (omfs_check_chain_cycle(dir, &slow, &fast)) + return true; } return true; } -- 2.43.0