From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 253F52DCF48; Tue, 8 Jul 2025 16:52:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751993564; cv=none; b=cSr2dNJVb4HYIS+PWVh9NQBwdKxJSL3CZpL0icgyeKQSEDcF0pqiC9Z1X6F50kXV3iwrVpaV1VzEfQMyVKjOlUTKwqbN9FFcaCpfbFC7/tSEkra4VCWWDRGRRXfPBuaGFTcqJUIJvaDq9jixxbzQSEcNOAALE+gF/JRFaDye06Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751993564; c=relaxed/simple; bh=eHJGnG0/PaC9Hg9EfcapPEOHFouI/LNkX9rFpNUDsmU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=O30MK535K0eML9DKW9PsstcOCjJ4hjNgE5X5cKFcdrjilRsL7np3ISntJZ+2289dM0zigQQ0yhXQrPCSb6OgQ7oXHRUCbazbL3d79CuAjTtGqQgWamm+aEI9it6UMD6mVAWoaFpXfBydk/NHf7jJmQagFmQ+8TGyT2f08bdOxZg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ic5m8yJA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Ic5m8yJA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A073EC4CEED; Tue, 8 Jul 2025 16:52:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751993564; bh=eHJGnG0/PaC9Hg9EfcapPEOHFouI/LNkX9rFpNUDsmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ic5m8yJAOaJAXzi4aD9zu63JtuHyc5wCSU2rwv2Dv6/WnkCPG3CRfqskdin88+eHr cBnv7WJXJtwFulmtQlNz3su4ehRNVY54By1H0Co0Skq+UQlF5AS7L9vjNMmgV3+Est gj7xKwGK/QBDv/mACi97LZcEk34fdT1xuCIO8oxo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, linux-cifs@vger.kernel.org, Pierguido Lambri , David Howells , Stefan Metzmacher , "Paulo Alcantara (Red Hat)" , Steve French , Sasha Levin Subject: [PATCH 6.15 118/178] smb: client: fix native SMB symlink traversal Date: Tue, 8 Jul 2025 18:22:35 +0200 Message-ID: <20250708162239.691314084@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250708162236.549307806@linuxfoundation.org> References: <20250708162236.549307806@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paulo Alcantara [ Upstream commit 3363da82e02f1bddc54faa92ea430c6532e2cd2e ] We've seen customers having shares mounted in paths like /??/C:/ or /??/UNC/foo.example.com/share in order to get their native SMB symlinks successfully followed from different mounts. After commit 12b466eb52d9 ("cifs: Fix creating and resolving absolute NT-style symlinks"), the client would then convert absolute paths from "/??/C:/" to "/mnt/c/" by default. The absolute paths would vary depending on the value of symlinkroot= mount option. Fix this by restoring old behavior of not trying to convert absolute paths by default. Only do this if symlinkroot= was _explicitly_ set. Before patch: $ mount.cifs //w22-fs0/test2 /mnt/1 -o vers=3.1.1,username=xxx,password=yyy $ ls -l /mnt/1/symlink2 lrwxr-xr-x 1 root root 15 Jun 20 14:22 /mnt/1/symlink2 -> /mnt/c/testfile $ mkdir -p /??/C:; echo foo > //??/C:/testfile $ cat /mnt/1/symlink2 cat: /mnt/1/symlink2: No such file or directory After patch: $ mount.cifs //w22-fs0/test2 /mnt/1 -o vers=3.1.1,username=xxx,password=yyy $ ls -l /mnt/1/symlink2 lrwxr-xr-x 1 root root 15 Jun 20 14:22 /mnt/1/symlink2 -> '/??/C:/testfile' $ mkdir -p /??/C:; echo foo > //??/C:/testfile $ cat /mnt/1/symlink2 foo Cc: linux-cifs@vger.kernel.org Reported-by: Pierguido Lambri Cc: David Howells Cc: Stefan Metzmacher Fixes: 12b466eb52d9 ("cifs: Fix creating and resolving absolute NT-style symlinks") Signed-off-by: Paulo Alcantara (Red Hat) Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/client/fs_context.c | 17 +++++++---------- fs/smb/client/reparse.c | 22 +++++++++++++--------- 2 files changed, 20 insertions(+), 19 deletions(-) diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c index a634a34d4086a..59ccc2229ab30 100644 --- a/fs/smb/client/fs_context.c +++ b/fs/smb/client/fs_context.c @@ -1824,10 +1824,14 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, cifs_errorf(fc, "symlinkroot mount options must be absolute path\n"); goto cifs_parse_mount_err; } - kfree(ctx->symlinkroot); - ctx->symlinkroot = kstrdup(param->string, GFP_KERNEL); - if (!ctx->symlinkroot) + if (strnlen(param->string, PATH_MAX) == PATH_MAX) { + cifs_errorf(fc, "symlinkroot path too long (max path length: %u)\n", + PATH_MAX - 1); goto cifs_parse_mount_err; + } + kfree(ctx->symlinkroot); + ctx->symlinkroot = param->string; + param->string = NULL; break; } /* case Opt_ignore: - is ignored as expected ... */ @@ -1837,13 +1841,6 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, goto cifs_parse_mount_err; } - /* - * By default resolve all native absolute symlinks relative to "/mnt/". - * Same default has drvfs driver running in WSL for resolving SMB shares. - */ - if (!ctx->symlinkroot) - ctx->symlinkroot = kstrdup("/mnt/", GFP_KERNEL); - return 0; cifs_parse_mount_err: diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c index 1c40e42e4d897..5fa29a97ac154 100644 --- a/fs/smb/client/reparse.c +++ b/fs/smb/client/reparse.c @@ -57,6 +57,7 @@ static int create_native_symlink(const unsigned int xid, struct inode *inode, struct reparse_symlink_data_buffer *buf = NULL; struct cifs_open_info_data data = {}; struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb); + const char *symroot = cifs_sb->ctx->symlinkroot; struct inode *new; struct kvec iov; __le16 *path = NULL; @@ -82,7 +83,8 @@ static int create_native_symlink(const unsigned int xid, struct inode *inode, .symlink_target = symlink_target, }; - if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && symname[0] == '/') { + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && + symroot && symname[0] == '/') { /* * This is a request to create an absolute symlink on the server * which does not support POSIX paths, and expects symlink in @@ -92,7 +94,7 @@ static int create_native_symlink(const unsigned int xid, struct inode *inode, * ensure compatibility of this symlink stored in absolute form * on the SMB server. */ - if (!strstarts(symname, cifs_sb->ctx->symlinkroot)) { + if (!strstarts(symname, symroot)) { /* * If the absolute Linux symlink target path is not * inside "symlinkroot" location then there is no way @@ -101,12 +103,12 @@ static int create_native_symlink(const unsigned int xid, struct inode *inode, cifs_dbg(VFS, "absolute symlink '%s' cannot be converted to NT format " "because it is outside of symlinkroot='%s'\n", - symname, cifs_sb->ctx->symlinkroot); + symname, symroot); rc = -EINVAL; goto out; } - len = strlen(cifs_sb->ctx->symlinkroot); - if (cifs_sb->ctx->symlinkroot[len-1] != '/') + len = strlen(symroot); + if (symroot[len - 1] != '/') len++; if (symname[len] >= 'a' && symname[len] <= 'z' && (symname[len+1] == '/' || symname[len+1] == '\0')) { @@ -782,6 +784,7 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len, const char *full_path, struct cifs_sb_info *cifs_sb) { + const char *symroot = cifs_sb->ctx->symlinkroot; char sep = CIFS_DIR_SEP(cifs_sb); char *linux_target = NULL; char *smb_target = NULL; @@ -815,7 +818,8 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len, goto out; } - if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && !relative) { + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && + symroot && !relative) { /* * This is an absolute symlink from the server which does not * support POSIX paths, so the symlink is in NT-style path. @@ -907,15 +911,15 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len, } abs_path_len = strlen(abs_path)+1; - symlinkroot_len = strlen(cifs_sb->ctx->symlinkroot); - if (cifs_sb->ctx->symlinkroot[symlinkroot_len-1] == '/') + symlinkroot_len = strlen(symroot); + if (symroot[symlinkroot_len - 1] == '/') symlinkroot_len--; linux_target = kmalloc(symlinkroot_len + 1 + abs_path_len, GFP_KERNEL); if (!linux_target) { rc = -ENOMEM; goto out; } - memcpy(linux_target, cifs_sb->ctx->symlinkroot, symlinkroot_len); + memcpy(linux_target, symroot, symlinkroot_len); linux_target[symlinkroot_len] = '/'; memcpy(linux_target + symlinkroot_len + 1, abs_path, abs_path_len); } else if (smb_target[0] == sep && relative) { -- 2.39.5