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ext4: ioctl: fix erroneous return value

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The ext4_ioctl_setflags() function which is used in the ioctls
EXT4_IOC_SETFLAGS and EXT4_IOC_FSSETXATTR may return the positive value
EPERM instead of -EPERM in case of error. This bug was introduced by a
recent commit 9b7365fc.

The following program can be used to illustrate the wrong behavior:

    #include <sys/types.h>
    #include <sys/ioctl.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <err.h>

    #define FS_IOC_GETFLAGS _IOR('f', 1, long)
    #define FS_IOC_SETFLAGS _IOW('f', 2, long)
    #define FS_IMMUTABLE_FL 0x00000010

    int main(void)
    {
        int fd;
        long flags;

        fd = open("file", O_RDWR|O_CREAT, 0600);
        if (fd < 0)
            err(1, "open");

        if (ioctl(fd, FS_IOC_GETFLAGS, &flags) < 0)
            err(1, "ioctl: FS_IOC_GETFLAGS");

        flags |= FS_IMMUTABLE_FL;

        if (ioctl(fd, FS_IOC_SETFLAGS, &flags) < 0)
            err(1, "ioctl: FS_IOC_SETFLAGS");

        warnx("ioctl returned no error");

        return 0;
    }

Running it gives the following result:

    $ strace -e ioctl ./test
    ioctl(3, FS_IOC_GETFLAGS, 0x7ffdbd8bfd38) = 0
    ioctl(3, FS_IOC_SETFLAGS, 0x7ffdbd8bfd38) = 1
    test: ioctl returned no error
    +++ exited with 0 +++

Running the program on a kernel with the bug fixed gives the proper result:

    $ strace -e ioctl ./test
    ioctl(3, FS_IOC_GETFLAGS, 0x7ffdd2768258) = 0
    ioctl(3, FS_IOC_SETFLAGS, 0x7ffdd2768258) = -1 EPERM (Operation not permitted)
    test: ioctl: FS_IOC_SETFLAGS: Operation not permitted
    +++ exited with 1 +++

Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Anton Protopopov 2016-02-11 23:57:21 -05:00 committed by Theodore Ts'o
parent 05145bd799
commit fdde368e7c
1 changed files with 1 additions and 1 deletions
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2
fs/ext4/ioctl.c
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@ -208,7 +208,7 @@ static int ext4_ioctl_setflags(struct inode *inode,
{
struct ext4_inode_info *ei = EXT4_I(inode);
handle_t *handle = NULL;
int err = EPERM, migrate = 0;
int err = -EPERM, migrate = 0;
struct ext4_iloc iloc;
unsigned int oldflags, mask, i;
unsigned int jflag;