From beff0bc9d69bc8e733f9bca28e2d3df5b3e10e42 Mon Sep 17 00:00:00 2001 From: Norbert Szetei Date: Sat, 29 Mar 2025 06:58:15 +0000 Subject: [PATCH] ksmbd: fix overflow in dacloffset bounds check The dacloffset field was originally typed as int and used in an unchecked addition, which could overflow and bypass the existing bounds check in both smb_check_perm_dacl() and smb_inherit_dacl(). This could result in out-of-bounds memory access and a kernel crash when dereferencing the DACL pointer. This patch converts dacloffset to unsigned int and uses check_add_overflow() to validate access to the DACL. Cc: stable@vger.kernel.org Signed-off-by: Norbert Szetei Acked-by: Namjae Jeon Signed-off-by: Steve French --- fs/smb/server/smbacl.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c index 49b128698670..2693ea2d67aa 100644 --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -1026,7 +1026,9 @@ int smb_inherit_dacl(struct ksmbd_conn *conn, struct dentry *parent = path->dentry->d_parent; struct mnt_idmap *idmap = mnt_idmap(path->mnt); int inherited_flags = 0, flags = 0, i, nt_size = 0, pdacl_size; - int rc = 0, dacloffset, pntsd_type, pntsd_size, acl_len, aces_size; + int rc = 0, pntsd_type, pntsd_size, acl_len, aces_size; + unsigned int dacloffset; + size_t dacl_struct_end; u16 num_aces, ace_cnt = 0; char *aces_base; bool is_dir = S_ISDIR(d_inode(path->dentry)->i_mode); @@ -1035,8 +1037,11 @@ int smb_inherit_dacl(struct ksmbd_conn *conn, parent, &parent_pntsd); if (pntsd_size <= 0) return -ENOENT; + dacloffset = le32_to_cpu(parent_pntsd->dacloffset); - if (!dacloffset || (dacloffset + sizeof(struct smb_acl) > pntsd_size)) { + if (!dacloffset || + check_add_overflow(dacloffset, sizeof(struct smb_acl), &dacl_struct_end) || + dacl_struct_end > (size_t)pntsd_size) { rc = -EINVAL; goto free_parent_pntsd; } @@ -1240,7 +1245,9 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path, struct smb_ntsd *pntsd = NULL; struct smb_acl *pdacl; struct posix_acl *posix_acls; - int rc = 0, pntsd_size, acl_size, aces_size, pdacl_size, dacl_offset; + int rc = 0, pntsd_size, acl_size, aces_size, pdacl_size; + unsigned int dacl_offset; + size_t dacl_struct_end; struct smb_sid sid; int granted = le32_to_cpu(*pdaccess & ~FILE_MAXIMAL_ACCESS_LE); struct smb_ace *ace; @@ -1259,7 +1266,8 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path, dacl_offset = le32_to_cpu(pntsd->dacloffset); if (!dacl_offset || - (dacl_offset + sizeof(struct smb_acl) > pntsd_size)) + check_add_overflow(dacl_offset, sizeof(struct smb_acl), &dacl_struct_end) || + dacl_struct_end > (size_t)pntsd_size) goto err_out; pdacl = (struct smb_acl *)((char *)pntsd + le32_to_cpu(pntsd->dacloffset));