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authorJosh Triplett <josh@joshtriplett.org>2014-04-03 14:48:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-03 16:21:05 -0700
commit69369a7003735d0d8ef22097e27a55a8bad9557a (patch)
treeb7638899a8e81fc18a497791685f1b571d733896
parent8f6c5ffc8987f4f5b5a3e9d557d94bbf3a9bf216 (diff)
fs, kernel: permit disabling the uselib syscall
uselib hasn't been used since libc5; glibc does not use it. Support turning it off. When disabled, also omit the load_elf_library implementation from binfmt_elf.c, which only uselib invokes. bloat-o-meter: add/remove: 0/4 grow/shrink: 0/1 up/down: 0/-785 (-785) function old new delta padzero 39 36 -3 uselib_flags 20 - -20 sys_uselib 168 - -168 SyS_uselib 168 - -168 load_elf_library 426 - -426 The new CONFIG_USELIB defaults to `y'. Signed-off-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/binfmt_elf.c9
-rw-r--r--fs/exec.c2
-rw-r--r--init/Kconfig10
-rw-r--r--kernel/sys_ni.c1
4 files changed, 21 insertions, 1 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 67be2951b98a..0f59799fa105 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -46,10 +46,15 @@
#endif
static int load_elf_binary(struct linux_binprm *bprm);
-static int load_elf_library(struct file *);
static unsigned long elf_map(struct file *, unsigned long, struct elf_phdr *,
int, int, unsigned long);
+#ifdef CONFIG_USELIB
+static int load_elf_library(struct file *);
+#else
+#define load_elf_library NULL
+#endif
+
/*
* If we don't support core dumping, then supply a NULL so we
* don't even try.
@@ -1005,6 +1010,7 @@ out_free_ph:
goto out;
}
+#ifdef CONFIG_USELIB
/* This is really simpleminded and specialized - we are loading an
a.out library that is given an ELF header. */
static int load_elf_library(struct file *file)
@@ -1083,6 +1089,7 @@ out_free_ph:
out:
return error;
}
+#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_ELF_CORE
/*
diff --git a/fs/exec.c b/fs/exec.c
index 4f59402fdda5..25dfeba6d55f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -97,6 +97,7 @@ static inline void put_binfmt(struct linux_binfmt * fmt)
module_put(fmt->module);
}
+#ifdef CONFIG_USELIB
/*
* Note that a shared library must be both readable and executable due to
* security reasons.
@@ -156,6 +157,7 @@ exit:
out:
return error;
}
+#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_MMU
/*
diff --git a/init/Kconfig b/init/Kconfig
index e45cc62904b3..8114a06117e3 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -273,6 +273,16 @@ config FHANDLE
get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
syscalls.
+config USELIB
+ bool "uselib syscall"
+ default y
+ help
+ This option enables the uselib syscall, a system call used in the
+ dynamic linker from libc5 and earlier. glibc does not use this
+ system call. If you intend to run programs built on libc5 or
+ earlier, you may need to enable this syscall. Current systems
+ running glibc can safely disable this.
+
config AUDIT
bool "Auditing support"
depends on NET
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 74395a95b7e9..bc8d1b74a6b9 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -152,6 +152,7 @@ cond_syscall(sys_process_vm_readv);
cond_syscall(sys_process_vm_writev);
cond_syscall(compat_sys_process_vm_readv);
cond_syscall(compat_sys_process_vm_writev);
+cond_syscall(sys_uselib);
/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);