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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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04d26e7b15
If no synflood happens for a long enough period of time, then the synflood timestamp isn't refreshed and jiffies can advance so much that time_after32() can't accurately compare them any more. Therefore, we can end up in a situation where time_after32(now, last_overflow + HZ) returns false, just because these two values are too far apart. In that case, the synflood timestamp isn't updated as it should be, which can trick tcp_synq_no_recent_overflow() into rejecting valid syncookies. For example, let's consider the following scenario on a system with HZ=1000: * The synflood timestamp is 0, either because that's the timestamp of the last synflood or, more commonly, because we're working with a freshly created socket. * We receive a new SYN, which triggers synflood protection. Let's say that this happens when jiffies == 2147484649 (that is, 'synflood timestamp' + HZ + 2^31 + 1). * Then tcp_synq_overflow() doesn't update the synflood timestamp, because time_after32(2147484649, 1000) returns false. With: - 2147484649: the value of jiffies, aka. 'now'. - 1000: the value of 'last_overflow' + HZ. * A bit later, we receive the ACK completing the 3WHS. But cookie_v[46]_check() rejects it because tcp_synq_no_recent_overflow() says that we're not under synflood. That's because time_after32(2147484649, 120000) returns false. With: - 2147484649: the value of jiffies, aka. 'now'. - 120000: the value of 'last_overflow' + TCP_SYNCOOKIE_VALID. Of course, in reality jiffies would have increased a bit, but this condition will last for the next 119 seconds, which is far enough to accommodate for jiffie's growth. Fix this by updating the overflow timestamp whenever jiffies isn't within the [last_overflow, last_overflow + HZ] range. That shouldn't have any performance impact since the update still happens at most once per second. Now we're guaranteed to have fresh timestamps while under synflood, so tcp_synq_no_recent_overflow() can safely use it with time_after32() in such situations. Stale timestamps can still make tcp_synq_no_recent_overflow() return the wrong verdict when not under synflood. This will be handled in the next patch. For 64 bits architectures, the problem was introduced with the conversion of ->tw_ts_recent_stamp to 32 bits integer by commitcca9bab1b7
("tcp: use monotonic timestamps for PAWS"). The problem has always been there on 32 bits architectures. Fixes:cca9bab1b7
("tcp: use monotonic timestamps for PAWS") Fixes:1da177e4c3
("Linux-2.6.12-rc2") Signed-off-by: Guillaume Nault <gnault@redhat.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
114 lines
3.7 KiB
C
114 lines
3.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_TIME_H
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#define _LINUX_TIME_H
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# include <linux/cache.h>
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# include <linux/seqlock.h>
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# include <linux/math64.h>
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# include <linux/time64.h>
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extern struct timezone sys_tz;
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int get_timespec64(struct timespec64 *ts,
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const struct __kernel_timespec __user *uts);
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int put_timespec64(const struct timespec64 *ts,
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struct __kernel_timespec __user *uts);
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int get_itimerspec64(struct itimerspec64 *it,
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const struct __kernel_itimerspec __user *uit);
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int put_itimerspec64(const struct itimerspec64 *it,
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struct __kernel_itimerspec __user *uit);
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extern time64_t mktime64(const unsigned int year, const unsigned int mon,
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const unsigned int day, const unsigned int hour,
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const unsigned int min, const unsigned int sec);
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/* Some architectures do not supply their own clocksource.
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* This is mainly the case in architectures that get their
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* inter-tick times by reading the counter on their interval
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* timer. Since these timers wrap every tick, they're not really
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* useful as clocksources. Wrapping them to act like one is possible
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* but not very efficient. So we provide a callout these arches
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* can implement for use with the jiffies clocksource to provide
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* finer then tick granular time.
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*/
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#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
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extern u32 (*arch_gettimeoffset)(void);
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#endif
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#ifdef CONFIG_POSIX_TIMERS
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extern void clear_itimer(void);
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#else
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static inline void clear_itimer(void) {}
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#endif
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extern long do_utimes(int dfd, const char __user *filename, struct timespec64 *times, int flags);
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/*
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* Similar to the struct tm in userspace <time.h>, but it needs to be here so
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* that the kernel source is self contained.
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*/
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struct tm {
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/*
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* the number of seconds after the minute, normally in the range
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* 0 to 59, but can be up to 60 to allow for leap seconds
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*/
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int tm_sec;
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/* the number of minutes after the hour, in the range 0 to 59*/
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int tm_min;
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/* the number of hours past midnight, in the range 0 to 23 */
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int tm_hour;
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/* the day of the month, in the range 1 to 31 */
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int tm_mday;
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/* the number of months since January, in the range 0 to 11 */
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int tm_mon;
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/* the number of years since 1900 */
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long tm_year;
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/* the number of days since Sunday, in the range 0 to 6 */
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int tm_wday;
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/* the number of days since January 1, in the range 0 to 365 */
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int tm_yday;
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};
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void time64_to_tm(time64_t totalsecs, int offset, struct tm *result);
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# include <linux/time32.h>
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static inline bool itimerspec64_valid(const struct itimerspec64 *its)
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{
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if (!timespec64_valid(&(its->it_interval)) ||
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!timespec64_valid(&(its->it_value)))
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return false;
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return true;
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}
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/**
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* time_after32 - compare two 32-bit relative times
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* @a: the time which may be after @b
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* @b: the time which may be before @a
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*
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* time_after32(a, b) returns true if the time @a is after time @b.
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* time_before32(b, a) returns true if the time @b is before time @a.
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*
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* Similar to time_after(), compare two 32-bit timestamps for relative
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* times. This is useful for comparing 32-bit seconds values that can't
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* be converted to 64-bit values (e.g. due to disk format or wire protocol
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* issues) when it is known that the times are less than 68 years apart.
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*/
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#define time_after32(a, b) ((s32)((u32)(b) - (u32)(a)) < 0)
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#define time_before32(b, a) time_after32(a, b)
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/**
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* time_between32 - check if a 32-bit timestamp is within a given time range
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* @t: the time which may be within [l,h]
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* @l: the lower bound of the range
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* @h: the higher bound of the range
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*
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* time_before32(t, l, h) returns true if @l <= @t <= @h. All operands are
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* treated as 32-bit integers.
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*
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* Equivalent to !(time_before32(@t, @l) || time_after32(@t, @h)).
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*/
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#define time_between32(t, l, h) ((u32)(h) - (u32)(l) >= (u32)(t) - (u32)(l))
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#endif
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