| Message ID | 20230724224857.2049906-1-sel4@tilde.club (mailing list archive) |
|---|---|
| State | Rejected |
| Headers | show |
| Series | fortify: strnlen: Call fortify_panic() only if the number of bytes read is greater than maxlen | expand |
On July 24, 2023 3:48:57 PM PDT, sel4@tilde.club wrote: >From: Brandon Luo <sel4@tilde.club> > >If the number of bytes read is p_size and p_size is less than maxlen, >fortify_panic() will be called incorrectly. Only panic if the number of >bytes read is greater than the minimum of p_size and maxlen since that is > the argument to __real_strnlen(). > >Reported-by: syzbot+98d3ceb7e01269e7bf4f@syzkaller.appspotmail.com >Closes: https://lore.kernel.org/all/000000000000d8352e0600c0c804@google.com/ > >Reported-by: syzbot+155274e882dcbf9885df@syzkaller.appspotmail.com >Closes: https://lore.kernel.org/all/000000000000de4c2c0600c02b28@google.com/ Thanks for looking at these, but strnlen is working correctly. The problem was hfs's overread of a cast be32 when used with strscpy. See: https://lore.kernel.org/lkml/202307182147.A5B81B67D@keescook/ -Kees > >Signed-off-by: Brandon Luo <sel4@tilde.club> >--- > include/linux/fortify-string.h | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > >diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h >index da51a83b2829..cde637f735fe 100644 >--- a/include/linux/fortify-string.h >+++ b/include/linux/fortify-string.h >@@ -176,8 +176,9 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size > } > > /* Do not check characters beyond the end of p. */ >- ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); >- if (p_size <= ret && maxlen != ret) >+ maxlen = (maxlen < p_size) ? maxlen : p_size; >+ ret = __real_strnlen(p, maxlen); >+ if (maxlen < ret) > fortify_panic(__func__); > return ret; > }
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index da51a83b2829..cde637f735fe 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -176,8 +176,9 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size } /* Do not check characters beyond the end of p. */ - ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); - if (p_size <= ret && maxlen != ret) + maxlen = (maxlen < p_size) ? maxlen : p_size; + ret = __real_strnlen(p, maxlen); + if (maxlen < ret) fortify_panic(__func__); return ret; }