From: Christian Göttsche cgzones@googlemail.com
[ Upstream commit 1b419c889c0767a5b66d0a6c566cae491f1cb0f7 ]
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 cgzones@googlemail.com Reviewed-by: Serge Hallyn serge@hallyn.com Reviewed-by: Jan Kara jack@suse.cz Link: https://patch.msgid.link/20250302160657.127253-2-cgoettsche@seltendoof.de Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/balloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 396474e9e2bff..3a2dfc59fb40f 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -641,8 +641,8 @@ 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))