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Merge pull request #25554 from enr0n/follow-on-25509

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oomd: only check prefix_uid when uid != 0
This commit is contained in:
Lennart Poettering
2022-12-01 12:04:23 +01:00
committed by GitHub
parent 73d88b806b 3c0562778b
commit f0c24a0ed8
3 changed files with 35 additions and 28 deletions
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8
man/systemd.resource-control.xml
View File

@@ -1101,10 +1101,10 @@ DeviceAllow=/dev/loop-control
only respect these extended attributes if the unit's cgroup is owned by root.</para>
<para>When calculating candidates to relieve memory pressure, <command>systemd-oomd</command>
will only respect these extended attributes if the unit's cgroup owner, and the
owner of the monitored ancestor cgroup are the same. For example, if <command>systemd-oomd</command>
is calculating candidates for <filename>-.slice</filename>, then extended attributes set
on descendants of <filename>/user.slice/user-1000.slice/user@1000.service/</filename>
will only respect these extended attributes if the unit's cgroup is owned by root, or if the
unit's cgroup owner, and the owner of the monitored ancestor cgroup are the same. For example,
if <command>systemd-oomd</command> is calculating candidates for <filename>-.slice</filename>,
then extended attributes set on descendants of <filename>/user.slice/user-1000.slice/user@1000.service/</filename>
will be ignored because the descendants are owned by UID 1000, and <filename>-.slice</filename>
is owned by UID 0. But, if calculating candidates for
<filename>/user.slice/user-1000.slice/user@1000.service/</filename>, then extended attributes set

48
src/oom/oomd-util.c
View File

@@ -145,7 +145,7 @@ bool oomd_swap_free_below(const OomdSystemContext *ctx, int threshold_permyriad)
}
int oomd_fetch_cgroup_oom_preference(OomdCGroupContext *ctx, const char *prefix) {
uid_t uid, prefix_uid;
uid_t uid;
int r;
assert(ctx);
@@ -160,28 +160,34 @@ int oomd_fetch_cgroup_oom_preference(OomdCGroupContext *ctx, const char *prefix)
if (r < 0)
return log_debug_errno(r, "Failed to get owner/group from %s: %m", ctx->path);
r = cg_get_owner(SYSTEMD_CGROUP_CONTROLLER, prefix, &prefix_uid);
if (r < 0)
return log_debug_errno(r, "Failed to get owner/group from %s: %m", ctx->path);
if (uid != 0) {
uid_t prefix_uid;
if (uid == prefix_uid || uid == 0) {
/* Ignore most errors when reading the xattr since it is usually unset and cgroup xattrs are only used
* as an optional feature of systemd-oomd (and the system might not even support them). */
r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_avoid");
if (r == -ENOMEM)
return log_oom_debug();
if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
log_debug_errno(r, "Failed to get xattr user.oomd_avoid, ignoring: %m");
ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_AVOID : ctx->preference;
r = cg_get_owner(SYSTEMD_CGROUP_CONTROLLER, prefix, &prefix_uid);
if (r < 0)
return log_debug_errno(r, "Failed to get owner/group from %s: %m", prefix);
r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_omit");
if (r == -ENOMEM)
return log_oom_debug();
if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
log_debug_errno(r, "Failed to get xattr user.oomd_omit, ignoring: %m");
ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_OMIT : ctx->preference;
} else
ctx->preference = MANAGED_OOM_PREFERENCE_NONE;
if (uid != prefix_uid) {
ctx->preference = MANAGED_OOM_PREFERENCE_NONE;
return 0;
}
}
/* Ignore most errors when reading the xattr since it is usually unset and cgroup xattrs are only used
* as an optional feature of systemd-oomd (and the system might not even support them). */
r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_avoid");
if (r == -ENOMEM)
return log_oom_debug();
if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
log_debug_errno(r, "Failed to get xattr user.oomd_avoid, ignoring: %m");
ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_AVOID : ctx->preference;
r = cg_get_xattr_bool(SYSTEMD_CGROUP_CONTROLLER, ctx->path, "user.oomd_omit");
if (r == -ENOMEM)
return log_oom_debug();
if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
log_debug_errno(r, "Failed to get xattr user.oomd_omit, ignoring: %m");
ctx->preference = r > 0 ? MANAGED_OOM_PREFERENCE_OMIT : ctx->preference;
return 0;
}

7
src/oom/oomd-util.h
View File

@@ -109,9 +109,10 @@ static inline int compare_swap_usage(OomdCGroupContext * const *c1, OomdCGroupCo
* Returns the number of sorted items; negative on error. */
int oomd_sort_cgroup_contexts(Hashmap *h, oomd_compare_t compare_func, const char *prefix, OomdCGroupContext ***ret);
/* If the cgroups represented by `ctx` and `prefix` are owned by the same user,
* then set `ctx->preference` using the `user.oomd_avoid` and `user.oomd_omit`
* xattrs. Otherwise, set `ctx->preference` to MANAGED_OOM_PREFERENCE_NONE.
/* If the the cgroup is owned by root, or the cgroups represented by `ctx` and
* `prefix` are owned by the same user, then set `ctx->preference` using the
* `user.oomd_avoid` and `user.oomd_omit` xattrs. Otherwise, set
* `ctx->preference` to MANAGED_OOM_PREFERENCE_NONE.
*
* If `prefix` is NULL or the empty string, it is treated as root. If `prefix`
* does not specify an ancestor cgroup of `ctx`, -EINVAL is returned. Returns