6.8-stable review patch. If anyone has any objections, please let me know.
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From: Jinjiang Tu tujinjiang@huawei.com
[ Upstream commit 3a9e567ca45fb5280065283d10d9a11f0db61d2b ]
Patch series "mm/ksm: fix ksm exec support for prctl", v4.
commit 3c6f33b7273a ("mm/ksm: support fork/exec for prctl") inherits MMF_VM_MERGE_ANY flag when a task calls execve(). However, it doesn't create the mm_slot, so ksmd will not try to scan this task. The first patch fixes the issue.
The second patch refactors to prepare for the third patch. The third patch extends the selftests of ksm to verfity the deduplication really happens after fork/exec inherits ths KSM setting.
This patch (of 3):
commit 3c6f33b7273a ("mm/ksm: support fork/exec for prctl") inherits MMF_VM_MERGE_ANY flag when a task calls execve(). Howerver, it doesn't create the mm_slot, so ksmd will not try to scan this task.
To fix it, allocate and add the mm_slot to ksm_mm_head in __bprm_mm_init() when the mm has MMF_VM_MERGE_ANY flag.
Link: https://lkml.kernel.org/r/20240328111010.1502191-1-tujinjiang@huawei.com Link: https://lkml.kernel.org/r/20240328111010.1502191-2-tujinjiang@huawei.com Fixes: 3c6f33b7273a ("mm/ksm: support fork/exec for prctl") Signed-off-by: Jinjiang Tu tujinjiang@huawei.com Reviewed-by: David Hildenbrand david@redhat.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Nanyong Sun sunnanyong@huawei.com Cc: Rik van Riel riel@surriel.com Cc: Stefan Roesch shr@devkernel.io Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/exec.c | 11 +++++++++++ include/linux/ksm.h | 13 +++++++++++++ 2 files changed, 24 insertions(+)
diff --git a/fs/exec.c b/fs/exec.c index 5ee2545c3e183..f11cfd7bce0b1 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -67,6 +67,7 @@ #include <linux/time_namespace.h> #include <linux/user_events.h> #include <linux/rseq.h> +#include <linux/ksm.h>
#include <linux/uaccess.h> #include <asm/mmu_context.h> @@ -267,6 +268,14 @@ static int __bprm_mm_init(struct linux_binprm *bprm) goto err_free; }
+ /* + * Need to be called with mmap write lock + * held, to avoid race with ksmd. + */ + err = ksm_execve(mm); + if (err) + goto err_ksm; + /* * Place the stack at the largest stack address the architecture * supports. Later, we'll move this to an appropriate place. We don't @@ -288,6 +297,8 @@ static int __bprm_mm_init(struct linux_binprm *bprm) bprm->p = vma->vm_end - sizeof(void *); return 0; err: + ksm_exit(mm); +err_ksm: mmap_write_unlock(mm); err_free: bprm->vma = NULL; diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 401348e9f92b4..7e2b1de3996ac 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -59,6 +59,14 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) return 0; }
+static inline int ksm_execve(struct mm_struct *mm) +{ + if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) + return __ksm_enter(mm); + + return 0; +} + static inline void ksm_exit(struct mm_struct *mm) { if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) @@ -107,6 +115,11 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) return 0; }
+static inline int ksm_execve(struct mm_struct *mm) +{ + return 0; +} + static inline void ksm_exit(struct mm_struct *mm) { }