The quilt patch titled Subject: mm: refactor mm_access() to not return NULL has been removed from the -mm tree. Its filename was mm-refactor-mm_access-to-not-return-null.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> Subject: mm: refactor mm_access() to not return NULL Date: Tue, 24 Sep 2024 21:10:23 +0100 mm_access() can return NULL if the mm is not found, but this is handled the same as an error in all callers, with some translating this into an -ESRCH error. Only proc_mem_open() returns NULL if no mm is found, however in this case it is clearer and makes more sense to explicitly handle the error. Additionally we take the opportunity to refactor the function to eliminate unnecessary nesting. Simplify things by simply returning -ESRCH if no mm is found - this both eliminates confusing use of the IS_ERR_OR_NULL() macro, and simplifies callers which would return -ESRCH by returning this error directly. [lorenzo.stoakes@xxxxxxxxxx: prefer neater pointer error comparison] Link: https://lkml.kernel.org/r/2fae1834-749a-45e1-8594-5e5979cf7103@lucifer.local Link: https://lkml.kernel.org/r/20240924201023.193135-1-lorenzo.stoakes@xxxxxxxxxx Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> Suggested-by: Arnd Bergmann <arnd@xxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/base.c | 26 ++++++++++++++------------ kernel/fork.c | 5 +++-- mm/madvise.c | 4 ++-- mm/process_vm_access.c | 4 ++-- 4 files changed, 21 insertions(+), 18 deletions(-) --- a/fs/proc/base.c~mm-refactor-mm_access-to-not-return-null +++ a/fs/proc/base.c @@ -832,19 +832,21 @@ static const struct file_operations proc struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode) { struct task_struct *task = get_proc_task(inode); - struct mm_struct *mm = ERR_PTR(-ESRCH); + struct mm_struct *mm; - if (task) { - mm = mm_access(task, mode | PTRACE_MODE_FSCREDS); - put_task_struct(task); + if (!task) + return ERR_PTR(-ESRCH); - if (!IS_ERR_OR_NULL(mm)) { - /* ensure this mm_struct can't be freed */ - mmgrab(mm); - /* but do not pin its memory */ - mmput(mm); - } - } + mm = mm_access(task, mode | PTRACE_MODE_FSCREDS); + put_task_struct(task); + + if (IS_ERR(mm)) + return mm == ERR_PTR(-ESRCH) ? NULL : mm; + + /* ensure this mm_struct can't be freed */ + mmgrab(mm); + /* but do not pin its memory */ + mmput(mm); return mm; } @@ -2208,7 +2210,7 @@ static int map_files_d_revalidate(struct goto out_notask; mm = mm_access(task, PTRACE_MODE_READ_FSCREDS); - if (IS_ERR_OR_NULL(mm)) + if (IS_ERR(mm)) goto out; if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) { --- a/kernel/fork.c~mm-refactor-mm_access-to-not-return-null +++ a/kernel/fork.c @@ -1546,8 +1546,9 @@ struct mm_struct *mm_access(struct task_ return ERR_PTR(err); mm = get_task_mm(task); - if (mm && mm != current->mm && - !ptrace_may_access(task, mode)) { + if (!mm) { + mm = ERR_PTR(-ESRCH); + } else if (mm != current->mm && !ptrace_may_access(task, mode)) { mmput(mm); mm = ERR_PTR(-EACCES); } --- a/mm/madvise.c~mm-refactor-mm_access-to-not-return-null +++ a/mm/madvise.c @@ -1511,8 +1511,8 @@ SYSCALL_DEFINE5(process_madvise, int, pi /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */ mm = mm_access(task, PTRACE_MODE_READ_FSCREDS); - if (IS_ERR_OR_NULL(mm)) { - ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; + if (IS_ERR(mm)) { + ret = PTR_ERR(mm); goto release_task; } --- a/mm/process_vm_access.c~mm-refactor-mm_access-to-not-return-null +++ a/mm/process_vm_access.c @@ -201,8 +201,8 @@ static ssize_t process_vm_rw_core(pid_t } mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); - if (!mm || IS_ERR(mm)) { - rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; + if (IS_ERR(mm)) { + rc = PTR_ERR(mm); /* * Explicitly map EACCES to EPERM as EPERM is a more * appropriate error code for process_vw_readv/writev _ Patches currently in -mm which might be from lorenzo.stoakes@xxxxxxxxxx are mm-pagewalk-add-the-ability-to-install-ptes.patch mm-add-pte_marker_guard-pte-marker.patch mm-madvise-implement-lightweight-guard-page-mechanism.patch tools-testing-update-tools-uapi-header-for-mman-commonh.patch selftests-mm-add-self-tests-for-guard-page-feature.patch mm-remove-unnecessary-page_table_lock-on-stack-expansion.patch