Re: [PATCH 1/1] eal/linux: reject mountpt shorter than --huge-dir

[Ashish Sadanandan <ashish.sadanandan@gmail.com>]

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 Please ignore this patch, I'll submit an updated one. I somehow managed to
only execute a subset of the fast-tests suite initially and didn't run
eal_flags_misc_autotest at all. Now I see that my proposed fix is flawed, I
will submit another try soon.

Sorry for the noise

On Tue, Jan 3, 2023 at 11:57 AM Ashish Sadanandan <
ashish.sadanandan@gmail.com> wrote:

> The code added for allowing --huge-dir to specify hugetlbfs
> sub-directories has a bug where it incorrectly matches mounts that
> contain a prefix of the specified --huge-dir.
>
> Consider --huge-dir=/dev/hugepages1G is passed to rte_eal_init. Given
> the following hugetlbfs mounts
>
> $ mount | grep hugetlbfs
> hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
> hugetlbfs on /dev/hugepages1G type hugetlbfs (rw,relatime,pagesize=1024M)
> hugetlbfs on /mnt/huge type hugetlbfs (rw,relatime,pagesize=2M)
>
> get_hugepage_dir is first called with hugepage_sz=2097152. While
> iterating over all mount points, /dev/hugepages is incorrectly
> determined to be a match because it's a prefix of --huge-dir. The caller
> then obtains an exclusive lock on --huge-dir.
>
> In the next call to get_hugepage_dir, hugepage_sz=1073741824. This call
> correctly determines /dev/hugepages1G is a match. The caller again
> attempts to obtain an exclusive lock on --huge-dir and deadlocks because
> it's already holding a lock.
>
> This has been corrected by rejecting the mount point being considered if
> its length is smaller than the specified --huge-dir.
>
> Fixes: 24d5a1ce6b85 ("eal/linux: allow hugetlbfs sub-directories")
> Cc: john.levon@nutanix.com
> Cc: stable@dpdk.org
> ---
>  lib/eal/linux/eal_hugepage_info.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/lib/eal/linux/eal_hugepage_info.c
> b/lib/eal/linux/eal_hugepage_info.c
> index a1b6cb31ff..fcc3d82fdf 100644
> --- a/lib/eal/linux/eal_hugepage_info.c
> +++ b/lib/eal/linux/eal_hugepage_info.c
> @@ -269,16 +269,19 @@ get_hugepage_dir(uint64_t hugepage_sz, char
> *hugedir, int len)
>                  * Ignore any mount that doesn't contain the --huge-dir
>                  * directory.
>                  */
> -               if (strncmp(internal_conf->hugepage_dir, splitstr[MOUNTPT],
> -                       strlen(splitstr[MOUNTPT])) != 0) {
> +               size_t mountpt_len = strlen(splitstr[MOUNTPT]);
> +
> +               if (strlen(internal_conf->hugepage_dir) > mountpt_len)
> +                       continue;
> +               else if (strncmp(internal_conf->hugepage_dir,
> splitstr[MOUNTPT],
> +                       mountpt_len) != 0)
>                         continue;
> -               }
>
>                 /*
>                  * We found a match, but only prefer it if it's a longer
> match
>                  * (so /mnt/1 is preferred over /mnt for matching
> /mnt/1/2)).
>                  */
> -               if (strlen(splitstr[MOUNTPT]) > strlen(found))
> +               if (mountpt_len > strlen(found))
>                         strlcpy(found, splitstr[MOUNTPT], len);
>         } /* end while fgets */
>
> --
> 2.27.0
>
>

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