On Mon, 08 Nov 2010 14:05:03 +0530
Suresh Jayaraman <sjayaraman@xxxxxxx> wrote:
> On 11/08/2010 10:21 AM, Steve French wrote:
>
> > On Sun, Nov 7, 2010 at 8:12 PM, Jeff Layton <jlayton@xxxxxxxxx> wrote:
> >> On Sun, 7 Nov 2010 16:44:46 +0000 (GMT)
> >> Kjell Rune Skaaraas <kjella79@xxxxxxxx> wrote:
> >>
> >>> After upgrading from 2.6.36 for other reasons, starting certain apps like wine utorrent.exe will cause a kernel oops. I run the x86_64 version of Ubuntu 10.10 with various modified packages all around and the 2.6.37-rc1 kernel from the kernel PPA team. I experienced the same with a kernel I tried compiling myself too.
> >>>
> >>> Nov ý7 17:25:50 wodan kernel: [77498.450787] BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> >>> Nov ý7 17:25:50 wodan kernel: [77498.450883] IP: [<ffffffffa0395729>] cifs_ioctl+0x39/0x2f0 [cifs]
>
> Does the below patch fixes your problem?
>
>
> From: Suresh Jayaraman <sjayaraman@xxxxxxx>
> Subject: [PATCH] cifs: fix a NULL pointer dereference in cifs_ioctl() when the fd is bad
>
> The commit ba00ba modified cifs_ioctl() to use tcon pointer in cifsFileInfo
> via tlink instead of cifs_sb->tcon. When the file handle is not valid the
> cifsFileInfo->tlink will be NULL. Fix this by getting the tcon pointer by
> calling cifs_sb_master_tcon().
>
> Here's a hackish reproducer:
>
> #include <fcntl.h>
> #include <sys/ioctl.h>
> #include <sys/stat.h>
> #include <sys/types.h>
> #include <unistd.h>
>
> #define CIFS_IOC_CHECKUMOUNT _IO(0xCF, 2)
>
> int main (int argc, char* argv[])
> {
> int fd = open (argv[1], O_RDWR);
>
> ioctl(fd, CIFS_IOC_CHECKUMOUNT);
>
> close(fd);
> return 0;
> }
>
> This program will cause an oops when called with cifs mount point as an
> argument. I have tested the fix with the reproducer and it no longer oopses.
>
> Reported-by: Kjell Rune <kjella79@xxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Signed-off-by: Suresh Jayaraman <sjayaraman@xxxxxxx>
> ---
> fs/cifs/ioctl.c | 6 ++----
> 1 files changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
> index 2fa22f2..b8f680a 100644
> --- a/fs/cifs/ioctl.c
> +++ b/fs/cifs/ioctl.c
> @@ -35,10 +35,10 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
> struct inode *inode = filep->f_dentry->d_inode;
> int rc = -ENOTTY; /* strange error - but the precedent */
> int xid;
> - struct cifs_sb_info *cifs_sb;
> + struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
> #ifdef CONFIG_CIFS_POSIX
> struct cifsFileInfo *pSMBFile = filep->private_data;
> - struct cifsTconInfo *tcon = tlink_tcon(pSMBFile->tlink);
> + struct cifsTconInfo *tcon = cifs_sb_master_tcon(cifs_sb);
> __u64 ExtAttrBits = 0;
> __u64 ExtAttrMask = 0;
> __u64 caps = le64_to_cpu(tcon->fsUnixInfo.Capability);
> @@ -48,8 +48,6 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
>
> cFYI(1, "ioctl file %p cmd %u arg %lu", filep, command, arg);
>
> - cifs_sb = CIFS_SB(inode->i_sb);
> -
> switch (command) {
> case CIFS_IOC_CHECKUMOUNT:
> cFYI(1, "User unmount attempted");
NAK. This will mean that you're allowing people to do ioctls against
files using other people's credentials. If this is the problem then the
correct fix is to make sure that a cifsFileInfo is allocated during
the open.
--
Jeff Layton <jlayton@xxxxxxxxx>
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