Messages in this thread | | | Subject | Re: [PATCH 5/8] scsi: lpfc: change snprintf to scnprintf for possible overflow | From | James Smart <> | Date | Tue, 15 Jan 2019 14:41:17 -0800 |
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On 1/14/2019 5:15 PM, Kees Cook wrote: > On Sat, Jan 12, 2019 at 7:29 AM Willy Tarreau<w@1wt.eu> wrote: >> From: Silvio Cesare<silvio.cesare@gmail.com> >> >> Change snprintf to scnprintf. There are generally two cases where using >> snprintf causes problems. >> >> 1) Uses of size += snprintf(buf, SIZE - size, fmt, ...) >> In this case, if snprintf would have written more characters than what the >> buffer size (SIZE) is, then size will end up larger than SIZE. In later >> uses of snprintf, SIZE - size will result in a negative number, leading >> to problems. Note that size might already be too large by using >> size = snprintf before the code reaches a case of size += snprintf. >> >> 2) If size is ultimately used as a length parameter for a copy back to user >> space, then it will potentially allow for a buffer overflow and information >> disclosure when size is greater than SIZE. When the size is used to index >> the buffer directly, we can have memory corruption. This also means when >> size = snprintf... is used, it may also cause problems since size may become >> large. Copying to userspace is mitigated by the HARDENED_USERCOPY kernel >> configuration. >> >> The solution to these issues is to use scnprintf which returns the number of >> characters actually written to the buffer, so the size variable will never >> exceed SIZE. >> >> Signed-off-by: Silvio Cesare<silvio.cesare@gmail.com> >> Cc: James Smart<james.smart@broadcom.com> >> Cc: Dick Kennedy<dick.kennedy@broadcom.com> >> Cc: Dan Carpenter<dan.carpenter@oracle.com> >> Cc: Kees Cook<keescook@chromium.org> >> Cc: Will Deacon<will.deacon@arm.com> >> Cc: Greg KH<greg@kroah.com> >> Signed-off-by: Willy Tarreau<w@1wt.eu> > I think this needs Cc: stable. > > Reviewed-by: Kees Cook<keescook@chromium.org> > > -Kees >
Reviewed-by: James Smart <james.smart@broadcom.com>
-- james
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