[PATCH] erofs-utils: lib: fix EINTR mishandling in erofs_io_read()

[Utkal Singh]

Subject: Re: [PATCH] erofs-utils: lib: fix EINTR mishandling in erofs_io_read()

On Sat, Mar 28, 2026 at 6:51 PM, Ajay Rajera wrote:
> Fix this by setting ret to 0 on EINTR before falling through,
> matching the existing pattern in __erofs_io_write() and erofs_io_pread().

Hi Ajay,

The fix is correct. Placing ret = 0 after the inner if-else is safe
because the else branch always returns, so the assignment is only
reachable on EINTR. It correctly handles the partial-read case too:
After a short read advances i and decrements bytes, a subsequent EINTR
leaves both unchanged via ret = 0 and the retry continues from the
right buffer position.

Reviewed-by: Utkal Singh <singhutkal015 at gmail.com>

On Sat, 28 Mar 2026 at 18:51, Ajay Rajera <newajay.11r at gmail.com> wrote:
>
> When read() is interrupted by a signal and returns -1 with
> errno == EINTR, erofs_io_read() falls through without zeroing
> ret. This causes `bytes -= ret` and `i += ret` to execute with
> ret == -1, corrupting the byte counter (bytes wraps around since
> it is size_t) and the offset. This can lead to incorrect reads
> or infinite loops.
>
> Fix this by setting ret to 0 on EINTR before falling through,
> matching the existing pattern in __erofs_io_write() and
> erofs_io_pread().
>
> Also fix inconsistent whitespace (spaces instead of tabs) on the
> closing brace and return statement.
>
> Signed-off-by: Ajay Rajera <newajay.11r at gmail.com>
> ---
>  lib/io.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/io.c b/lib/io.c
> index 0c5eb2c..dd5e304 100644
> --- a/lib/io.c
> +++ b/lib/io.c
> @@ -551,11 +551,12 @@ ssize_t erofs_io_read(struct erofs_vfile *vf, void *buf, size_t bytes)
>                                           strerror(errno));
>                                 return -errno;
>                         }
> +                       ret = 0;
>                 }
>                 bytes -= ret;
>                 i += ret;
> -        }
> -        return i;
> +       }
> +       return i;
>  }
>
>  ssize_t erofs_io_write(struct erofs_vfile *vf, void *buf, size_t len)
> --
> 2.51.0.windows.1
>
>