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    Subject[PATCH v2 05/10] audit: allow audit code to satisfy getname requests from its names_list
    Date
    Currently, if we call getname() on a userland string more than once,
    we'll get multiple copies of the string and multiple audit_names
    records.

    Add a function that will allow the audit_names code to satisfy getname
    requests using info from the audit_names list, avoiding a new allocation
    and audit_names records.

    Signed-off-by: Jeff Layton <jlayton@redhat.com>
    ---
    fs/namei.c | 4 ++++
    include/linux/audit.h | 8 ++++++++
    kernel/auditsc.c | 23 +++++++++++++++++++++++
    3 files changed, 35 insertions(+)

    diff --git a/fs/namei.c b/fs/namei.c
    index 60db390..01a2dd18 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -130,6 +130,10 @@ getname_flags(const char __user *filename, int flags, int *empty)
    char *kname;
    int len;

    + result = audit_reusename(filename);
    + if (result)
    + return result;
    +
    /* FIXME: create dedicated slabcache? */
    result = kzalloc(sizeof(*result), GFP_KERNEL);
    if (unlikely(!result))
    diff --git a/include/linux/audit.h b/include/linux/audit.h
    index d361921..ea58de3 100644
    --- a/include/linux/audit.h
    +++ b/include/linux/audit.h
    @@ -469,6 +469,7 @@ extern void __audit_syscall_entry(int arch,
    int major, unsigned long a0, unsigned long a1,
    unsigned long a2, unsigned long a3);
    extern void __audit_syscall_exit(int ret_success, long ret_value);
    +extern struct getname_info *__audit_reusename(const __user char *uptr);
    extern void __audit_getname(struct getname_info *ginfo);
    extern void audit_putname(struct getname_info *ginfo);
    extern void __audit_inode(const char *name, const struct dentry *dentry,
    @@ -505,6 +506,12 @@ static inline void audit_syscall_exit(void *pt_regs)
    __audit_syscall_exit(success, return_code);
    }
    }
    +static inline struct getname_info *audit_reusename(const __user char *name)
    +{
    + if (unlikely(!audit_dummy_context()))
    + return __audit_reusename(name);
    + return NULL;
    +}
    static inline void audit_getname(struct getname_info *name)
    {
    if (unlikely(!audit_dummy_context()))
    @@ -642,6 +649,7 @@ extern int audit_signals;
    #define audit_syscall_entry(ta,a,b,c,d,e) do { ; } while (0)
    #define audit_syscall_exit(r) do { ; } while (0)
    #define audit_dummy_context() 1
    +#define audit_reusename(g) ({ NULL; })
    #define audit_getname(n) do { ; } while (0)
    #define audit_putname(n) do { ; } while (0)
    #define __audit_inode(n,d,p) do { ; } while (0)
    diff --git a/kernel/auditsc.c b/kernel/auditsc.c
    index 0ba346b..89974ca 100644
    --- a/kernel/auditsc.c
    +++ b/kernel/auditsc.c
    @@ -2035,6 +2035,29 @@ static struct audit_names *audit_alloc_name(struct audit_context *context,
    }

    /**
    + * audit_reusename - fill out getname_info with info from existing entry
    + * @uptr: userland ptr to pathname
    + *
    + * Search the audit_names list for the current audit context. If there is an
    + * existing entry with a matching "uptr" then return the getname_info
    + * associated with that audit_name. If not, return NULL.
    + */
    +struct getname_info *
    +__audit_reusename(const __user char *uptr)
    +{
    + struct audit_context *context = current->audit_context;
    + struct audit_names *n;
    +
    + list_for_each_entry(n, &context->names_list, list) {
    + if (!n->ginfo)
    + continue;
    + if (n->ginfo->uptr == uptr)
    + return n->ginfo;
    + }
    + return NULL;
    +}
    +
    +/**
    * audit_getname - add a name to the list
    * @name: name to add
    *
    --
    1.7.11.4


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