From: Christian Göttsche Date: Sun, 2 Mar 2025 16:06:39 +0000 (+0100) Subject: ext4: reorder capability check last X-Git-Tag: v6.15-rc1~145^2~11 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1b419c889c0767a5b66d0a6c566cae491f1cb0f7;p=thirdparty%2Fkernel%2Flinux.git ext4: reorder capability check last capable() calls refer to enabled LSMs whether to permit or deny the request. This is relevant in connection with SELinux, where a capability check results in a policy decision and by default a denial message on insufficient permission is issued. It can lead to three undesired cases: 1. A denial message is generated, even in case the operation was an unprivileged one and thus the syscall succeeded, creating noise. 2. To avoid the noise from 1. the policy writer adds a rule to ignore those denial messages, hiding future syscalls, where the task performs an actual privileged operation, leading to hidden limited functionality of that task. 3. To avoid the noise from 1. the policy writer adds a rule to permit the task the requested capability, while it does not need it, violating the principle of least privilege. Signed-off-by: Christian Göttsche Reviewed-by: Serge Hallyn Reviewed-by: Jan Kara Link: https://patch.msgid.link/20250302160657.127253-2-cgoettsche@seltendoof.de Signed-off-by: Theodore Ts'o --- diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 8042ad8738089..c48fd36b2d74c 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -649,8 +649,8 @@ static int ext4_has_free_clusters(struct ext4_sb_info *sbi, /* Hm, nope. Are (enough) root reserved clusters available? */ if (uid_eq(sbi->s_resuid, current_fsuid()) || (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) || - capable(CAP_SYS_RESOURCE) || - (flags & EXT4_MB_USE_ROOT_BLOCKS)) { + (flags & EXT4_MB_USE_ROOT_BLOCKS) || + capable(CAP_SYS_RESOURCE)) { if (free_clusters >= (nclusters + dirty_clusters + resv_clusters))