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From: Takuya Yoshikawa on 28 May 2010 04:00
Hi, I found some places in bin_elf_fdpic at which clear_user() is
incorrectly handled, by chance, when I was trying to check how to
use clear_user().

IIUC, the following commit was not correct.

commit ab4ad55512e95b68ca3e25516068e18874f89252
bin_elf_fdpic: check the return value of clear_user

Although I don't have an appropriate test box for this, I wrote a
simple patch to fix this. So if this is worth fixing, please pick
this up.

Thanks,
Takuya

===
clear_user() returns the number of bytes, unsigned long, that could not
be copied. So we should return -EFAULT rather than directly return the results.

Without this patch, positive values may be passed to elf_fdpic_map_file() and
the following error handlings do not function as expected.

1.
ret = elf_fdpic_map_file_constdisp_on_uclinux(params, file, mm);
if (ret < 0)
return ret;
2.
ret = elf_fdpic_map_file_by_direct_mmap(params, file, mm);
if (ret < 0)
return ret;

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya(a)oss.ntt.co.jp>
CC: Alexander Viro <viro(a)zeniv.linux.org.uk>
CC: Andrew Morton <akpm(a)linux-foundation.org>
CC: Daisuke HATAYAMA <d.hatayama(a)jp.fujitsu.com>
CC: David Howells <dhowells(a)redhat.com>
CC: Mike Frysinger <vapier(a)gentoo.org>
CC: Paul Mundt <lethal(a)linux-sh.org>
---
fs/binfmt_elf_fdpic.c | 26 +++++++++++---------------
1 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 2c5f9a0..63039ed 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -990,10 +990,9 @@ static int elf_fdpic_map_file_constdisp_on_uclinux(

/* clear any space allocated but not loaded */
if (phdr->p_filesz < phdr->p_memsz) {
- ret = clear_user((void *) (seg->addr + phdr->p_filesz),
- phdr->p_memsz - phdr->p_filesz);
- if (ret)
- return ret;
+ if (clear_user((void *) (seg->addr + phdr->p_filesz),
+ phdr->p_memsz - phdr->p_filesz))
+ return -EFAULT;
}

if (mm) {
@@ -1027,7 +1026,7 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
struct elf32_fdpic_loadseg *seg;
struct elf32_phdr *phdr;
unsigned long load_addr, delta_vaddr;
- int loop, dvset, ret;
+ int loop, dvset;

load_addr = params->load_addr;
delta_vaddr = 0;
@@ -1127,9 +1126,8 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
* PT_LOAD */
if (prot & PROT_WRITE && disp > 0) {
kdebug("clear[%d] ad=%lx sz=%lx", loop, maddr, disp);
- ret = clear_user((void __user *) maddr, disp);
- if (ret)
- return ret;
+ if (clear_user((void __user *) maddr, disp))
+ return -EFAULT;
maddr += disp;
}

@@ -1164,19 +1162,17 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
if (prot & PROT_WRITE && excess1 > 0) {
kdebug("clear[%d] ad=%lx sz=%lx",
loop, maddr + phdr->p_filesz, excess1);
- ret = clear_user((void __user *) maddr + phdr->p_filesz,
- excess1);
- if (ret)
- return ret;
+ if (clear_user((void __user *) maddr + phdr->p_filesz,
+ excess1))
+ return -EFAULT;
}

#else
if (excess > 0) {
kdebug("clear[%d] ad=%lx sz=%lx",
loop, maddr + phdr->p_filesz, excess);
- ret = clear_user((void *) maddr + phdr->p_filesz, excess);
- if (ret)
- return ret;
+ if (clear_user((void *) maddr + phdr->p_filesz, excess))
+ return -EFAULT;
}
#endif

--
1.7.0.4

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