From: "Eric W. Biederman" ebiederm@xmission.com
stable inclusion from stable-v5.10.220 commit ddb21f9984209b2c502ed28698918975528721f5 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAGEF4 CVE: CVE-2024-41020
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit bebf684bf330915e6c96313ad7db89a5480fc9c2 ]
The function fcheck despite it's comment is poorly named as it has no callers that only check it's return value. All of fcheck's callers use the returned file descriptor. The same is true for fcheck_files and __fcheck_files.
A new less confusing name is needed. In addition the names of these functions are confusing as they do not report the kind of locks that are needed to be held when these functions are called making error prone to use them.
To remedy this I am making the base functio name lookup_fd and will and prefixes and sufficies to indicate the rest of the context.
Name the function (previously called __fcheck_files) that proceeds from a struct files_struct, looks up the struct file of a file descriptor, and requires it's callers to verify all of the appropriate locks are held files_lookup_fd_raw.
The need for better names became apparent in the last round of discussion of this set of changes[1].
[1] https://lkml.kernel.org/r/CAHk-=wj8BQbgJFLa+J0e=iT-1qpmCRTbPAJ8gd6MJQ=kbRPqy... Link: https://lkml.kernel.org/r/20201120231441.29911-7-ebiederm@xmission.com Signed-off-by: Eric W. Biederman ebiederm@xmission.com [ cel: adjusted to apply to v5.10.y ] Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yifan Qiao qiaoyifan4@huawei.com --- include/linux/fdtable.h | 4 ++-- fs/file.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index e2df70d7bcc3..4b4410fc1282 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -81,7 +81,7 @@ struct dentry; /* * The caller must ensure that fd table isn't shared or hold rcu or file lock */ -static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd) +static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd) { struct fdtable *fdt = rcu_dereference_raw(files->fdt);
@@ -97,7 +97,7 @@ static inline struct file *fcheck_files(struct files_struct *files, unsigned int RCU_LOCKDEP_WARN(!rcu_read_lock_held() && !lockdep_is_held(&files->file_lock), "suspicious rcu_dereference_check() usage"); - return __fcheck_files(files, fd); + return files_lookup_fd_raw(files, fd); }
/* diff --git a/fs/file.c b/fs/file.c index 79968149b863..a35374680ff2 100644 --- a/fs/file.c +++ b/fs/file.c @@ -926,7 +926,7 @@ static struct file *__fget_files(struct files_struct *files, unsigned int fd, file = NULL; else if (!get_file_rcu_many(file, refs)) goto loop; - else if (__fcheck_files(files, fd) != file) { + else if (files_lookup_fd_raw(files, fd) != file) { fput_many(file, refs); goto loop; } @@ -993,7 +993,7 @@ static unsigned long __fget_light(unsigned int fd, fmode_t mask) struct file *file;
if (atomic_read(&files->count) == 1) { - file = __fcheck_files(files, fd); + file = files_lookup_fd_raw(files, fd); if (!file || unlikely(file->f_mode & mask)) return 0; return (unsigned long)file;