From: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
[ 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@xxxxxxxxxxxxxx>
Reviewed-by: Serge Hallyn <serge@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://patch.msgid.link/20250302160657.127253-2-cgoettsche@xxxxxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 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))
--
2.39.5
