mm/mempolicy.c: fix out of bounds write in mpol_parse_str()
commitc7a91bc7c2
upstream. What we are trying to do is change the '=' character to a NUL terminator and then at the end of the function we restore it back to an '='. The problem is there are two error paths where we jump to the end of the function before we have replaced the '=' with NUL. We end up putting the '=' in the wrong place (possibly one element before the start of the buffer). Link: http://lkml.kernel.org/r/20200115055426.vdjwvry44nfug7yy@kili.mountain Reported-by: syzbot+e64a13c5369a194d67df@syzkaller.appspotmail.com Fixes:095f1fc4eb
("mempolicy: rework shmem mpol parsing and display") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Dmitry Vyukov <dvyukov@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -2802,6 +2802,9 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
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char *flags = strchr(str, '=');
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int err = 1, mode;
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if (flags)
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*flags++ = '\0'; /* terminate mode string */
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if (nodelist) {
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/* NUL-terminate mode or flags string */
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*nodelist++ = '\0';
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@ -2812,9 +2815,6 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
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} else
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nodes_clear(nodes);
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if (flags)
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*flags++ = '\0'; /* terminate mode string */
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mode = match_string(policy_modes, MPOL_MAX, str);
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if (mode < 0)
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goto out;
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