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    Subject[PATCH RFC 3/4] fs/binfmt_elf: Tell user-space about the DENY_WRITE_EXEC personality flag
    Date
    Since personality() accepts any flags and does not mask out any unknown
    bits, inform user space that such personality flag is supported via an
    AT_FLAGS_DENY_WRITE_EXEC flag.

    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Cc: Eric Biederman <ebiederm@xmission.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Christoph Hellwig <hch@infradead.org>
    ---
    fs/binfmt_elf.c | 2 ++
    include/uapi/linux/binfmts.h | 4 ++++
    2 files changed, 6 insertions(+)

    diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
    index 6556e13ed95f..4e6cba1f67ee 100644
    --- a/fs/binfmt_elf.c
    +++ b/fs/binfmt_elf.c
    @@ -265,6 +265,8 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec,
    NEW_AUX_ENT(AT_BASE, interp_load_addr);
    if (bprm->interp_flags & BINPRM_FLAGS_PRESERVE_ARGV0)
    flags |= AT_FLAGS_PRESERVE_ARGV0;
    + if (IS_ENABLED(CONFIG_ARCH_ENABLE_DENY_WRITE_EXEC))
    + flags |= AT_FLAGS_DENY_WRITE_EXEC;
    NEW_AUX_ENT(AT_FLAGS, flags);
    NEW_AUX_ENT(AT_ENTRY, e_entry);
    NEW_AUX_ENT(AT_UID, from_kuid_munged(cred->user_ns, cred->uid));
    diff --git a/include/uapi/linux/binfmts.h b/include/uapi/linux/binfmts.h
    index c6f9450efc12..304bbb30264c 100644
    --- a/include/uapi/linux/binfmts.h
    +++ b/include/uapi/linux/binfmts.h
    @@ -22,4 +22,8 @@ struct pt_regs;
    #define AT_FLAGS_PRESERVE_ARGV0_BIT 0
    #define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT)

    +/* support for DENY_WRITE_EXEC personality flag */
    +#define AT_FLAGS_DENY_WRITE_EXEC_BIT 1
    +#define AT_FLAGS_DENY_WRITE_EXEC (1 << AT_FLAGS_DENY_WRITE_EXEC_BIT)
    +
    #endif /* _UAPI_LINUX_BINFMTS_H */
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