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    Subject[PATCH 4.19 220/220] x86/resctrl: Fix rdt_find_domain() return value and checks
    Date
    From: Reinette Chatre <reinette.chatre@intel.com>

    [ Upstream commit 52eb74339a6233c69f4e3794b69ea7c98eeeae1b ]

    rdt_find_domain() returns an ERR_PTR() that is generated from a provided
    domain id when the value is negative.

    Care needs to be taken when creating an ERR_PTR() from this value
    because a subsequent check using IS_ERR() expects the error to
    be within the MAX_ERRNO range. Using an invalid domain id as an
    ERR_PTR() does work at this time since this is currently always -1.
    Using this undocumented assumption is fragile since future users of
    rdt_find_domain() may not be aware of thus assumption.

    Two related issues are addressed:

    - Ensure that rdt_find_domain() always returns a valid error value by
    forcing the error to be -ENODEV when a negative domain id is provided.

    - In a few instances the return value of rdt_find_domain() is just
    checked for NULL - fix these to include a check of ERR_PTR.

    Fixes: d89b7379015f ("x86/intel_rdt/cqm: Add mon_data")
    Fixes: 521348b011d6 ("x86/intel_rdt: Introduce utility to obtain CDP peer")
    Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: fenghua.yu@intel.com
    Cc: gavin.hindman@intel.com
    Cc: jithu.joseph@intel.com
    Cc: x86-ml <x86@kernel.org>
    Link: https://lkml.kernel.org/r/b88cd4ff6a75995bf8db9b0ea546908fe50f69f3.1544479852.git.reinette.chatre@intel.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kernel/cpu/intel_rdt.c | 2 +-
    arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c | 2 +-
    arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 2 +-
    3 files changed, 3 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
    index abb71ac704433..cc43c5abd187b 100644
    --- a/arch/x86/kernel/cpu/intel_rdt.c
    +++ b/arch/x86/kernel/cpu/intel_rdt.c
    @@ -421,7 +421,7 @@ struct rdt_domain *rdt_find_domain(struct rdt_resource *r, int id,
    struct list_head *l;

    if (id < 0)
    - return ERR_PTR(id);
    + return ERR_PTR(-ENODEV);

    list_for_each(l, &r->domains) {
    d = list_entry(l, struct rdt_domain, list);
    diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
    index 627e5c809b33d..968ace3c6d730 100644
    --- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
    +++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
    @@ -459,7 +459,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)

    r = &rdt_resources_all[resid];
    d = rdt_find_domain(r, domid, NULL);
    - if (!d) {
    + if (IS_ERR_OR_NULL(d)) {
    ret = -ENOENT;
    goto out;
    }
    diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
    index 0d8ea82acd930..ad64031e82dcd 100644
    --- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
    +++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
    @@ -1023,7 +1023,7 @@ static int rdt_cdp_peer_get(struct rdt_resource *r, struct rdt_domain *d,
    * peer RDT CDP resource. Hence the WARN.
    */
    _d_cdp = rdt_find_domain(_r_cdp, d->id, NULL);
    - if (WARN_ON(!_d_cdp)) {
    + if (WARN_ON(IS_ERR_OR_NULL(_d_cdp))) {
    _r_cdp = NULL;
    ret = -EINVAL;
    }
    --
    2.20.1


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