• Arnd Bergmann's avatar
    remove lots of IS_ERR_VALUE abuses · 287980e4
    Arnd Bergmann authored
    Most users of IS_ERR_VALUE() in the kernel are wrong, as they
    pass an 'int' into a function that takes an 'unsigned long'
    argument. This happens to work because the type is sign-extended
    on 64-bit architectures before it gets converted into an
    unsigned type.
    
    However, anything that passes an 'unsigned short' or 'unsigned int'
    argument into IS_ERR_VALUE() is guaranteed to be broken, as are
    8-bit integers and types that are wider than 'unsigned long'.
    
    Andrzej Hajda has already fixed a lot of the worst abusers that
    were causing actual bugs, but it would be nice to prevent any
    users that are not passing 'unsigned long' arguments.
    
    This patch changes all users of IS_ERR_VALUE() that I could find
    on 32-bit ARM randconfig builds and x86 allmodconfig. For the
    moment, this doesn't change the definition of IS_ERR_VALUE()
    because there are probably still architecture specific users
    elsewhere.
    
    Almost all the warnings I got are for files that are better off
    using 'if (err)' or 'if (err < 0)'.
    The only legitimate user I could find that we get a warning for
    is the (32-bit only) freescale fman driver, so I did not remove
    the IS_ERR_VALUE() there but changed the type to 'unsigned long'.
    For 9pfs, I just worked around one user whose calling conventions
    are so obscure that I did not dare change the behavior.
    
    I was using this definition for testing:
    
     #define IS_ERR_VALUE(x) ((unsigned long*)NULL == (typeof (x)*)NULL && \
           unlikely((unsigned long long)(x) >= (unsigned long long)(typeof(x))-MAX_ERRNO))
    
    which ends up making all 16-bit or wider types work correctly with
    the most plausible interpretation of what IS_ERR_VALUE() was supposed
    to return according to its users, but also causes a compile-time
    warning for any users that do not pass an 'unsigned long' argument.
    
    I suggested this approach earlier this year, but back then we ended
    up deciding to just fix the users that are obviously broken. After
    the initial warning that caused me to get involved in the discussion
    (fs/gfs2/dir.c) showed up again in the mainline kernel, Linus
    asked me to send the whole thing again.
    
    [ Updated the 9p parts as per Al Viro  - Linus ]
    Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
    Cc: Andrzej Hajda <a.hajda@samsung.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Link: https://lkml.org/lkml/2016/1/7/363
    Link: https://lkml.org/lkml/2016/5/27/486
    Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> # For nvmem part
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    287980e4
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