sysctl: simplify unsigned int support
Commite7d316a02f("sysctl: handle error writing UINT_MAX to u32 fields") added proc_douintvec() to start help adding support for unsigned int, this however was only half the work needed. Two fixes have come in since then for the following issues: o Printing the values shows a negative value, this happens since do_proc_dointvec() and this uses proc_put_long() This was fixed by commit5380e5644a("sysctl: don't print negative flag for proc_douintvec"). o We can easily wrap around the int values: UINT_MAX is 4294967295, if we echo in 4294967295 + 1 we end up with 0, using 4294967295 + 2 we end up with 1. o We echo negative values in and they are accepted This was fixed by commit425fffd886("sysctl: report EINVAL if value is larger than UINT_MAX for proc_douintvec"). It still also failed to be added to sysctl_check_table()... instead of adding it with the current implementation just provide a proper and simplified unsigned int support without any array unsigned int support with no negative support at all. Historically sysctl proc helpers have supported arrays, due to the complexity this adds though we've taken a step back to evaluate array users to determine if its worth upkeeping for unsigned int. An evaluation using Coccinelle has been done to perform a grammatical search to ask ourselves: o How many sysctl proc_dointvec() (int) users exist which likely should be moved over to proc_douintvec() (unsigned int) ? Answer: about 8 - Of these how many are array users ? Answer: Probably only 1 o How many sysctl array users exist ? Answer: about 12 This last question gives us an idea just how popular arrays: they are not. Array support should probably just be kept for strings. The identified uint ports are: drivers/infiniband/core/ucma.c - max_backlog drivers/infiniband/core/iwcm.c - default_backlog net/core/sysctl_net_core.c - rps_sock_flow_sysctl() net/netfilter/nf_conntrack_timestamp.c - nf_conntrack_timestamp -- bool net/netfilter/nf_conntrack_acct.c nf_conntrack_acct -- bool net/netfilter/nf_conntrack_ecache.c - nf_conntrack_events -- bool net/netfilter/nf_conntrack_helper.c - nf_conntrack_helper -- bool net/phonet/sysctl.c proc_local_port_range() The only possible array users is proc_local_port_range() but it does not seem worth it to add array support just for this given the range support works just as well. Unsigned int support should be desirable more for when you *need* more than INT_MAX or using int min/max support then does not suffice for your ranges. If you forget and by mistake happen to register an unsigned int proc entry with an array, the driver will fail and you will get something as follows: sysctl table check failed: debug/test_sysctl//uint_0002 array now allowed CPU: 2 PID: 1342 Comm: modprobe Tainted: G W E <etc> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS <etc> Call Trace: dump_stack+0x63/0x81 __register_sysctl_table+0x350/0x650 ? kmem_cache_alloc_trace+0x107/0x240 __register_sysctl_paths+0x1b3/0x1e0 ? 0xffffffffc005f000 register_sysctl_table+0x1f/0x30 test_sysctl_init+0x10/0x1000 [test_sysctl] do_one_initcall+0x52/0x1a0 ? kmem_cache_alloc_trace+0x107/0x240 do_init_module+0x5f/0x200 load_module+0x1867/0x1bd0 ? __symbol_put+0x60/0x60 SYSC_finit_module+0xdf/0x110 SyS_finit_module+0xe/0x10 entry_SYSCALL_64_fastpath+0x1e/0xad RIP: 0033:0x7f042b22d119 <etc> Fixes:e7d316a02f("sysctl: handle error writing UINT_MAX to u32 fields") Link: http://lkml.kernel.org/r/20170519033554.18592-5-mcgrof@kernel.org Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Suggested-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> Cc: Liping Zhang <zlpnobody@gmail.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Cc: Kees Cook <keescook@chromium.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Luis R. Rodriguez
Linus Torvalds
parent
d383d48470
commit
4f2fec00af
2 changed files with 160 additions and 7 deletions
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@ -1061,6 +1061,18 @@ static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
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return -EINVAL;
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}
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static int sysctl_check_table_array(const char *path, struct ctl_table *table)
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{
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int err = 0;
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if (table->proc_handler == proc_douintvec) {
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if (table->maxlen != sizeof(unsigned int))
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err |= sysctl_err(path, table, "array now allowed");
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}
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return err;
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}
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static int sysctl_check_table(const char *path, struct ctl_table *table)
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{
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int err = 0;
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@ -1081,6 +1093,8 @@ static int sysctl_check_table(const char *path, struct ctl_table *table)
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err |= sysctl_err(path, table, "No data");
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if (!table->maxlen)
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err |= sysctl_err(path, table, "No maxlen");
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else
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err |= sysctl_check_table_array(path, table);
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}
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if (!table->proc_handler)
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err |= sysctl_err(path, table, "No proc_handler");
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153
kernel/sysctl.c
153
kernel/sysctl.c
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@ -2175,19 +2175,18 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
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return 0;
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}
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static int do_proc_douintvec_conv(bool *negp, unsigned long *lvalp,
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int *valp,
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int write, void *data)
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static int do_proc_douintvec_conv(unsigned long *lvalp,
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unsigned int *valp,
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int write, void *data)
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{
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if (write) {
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if (*negp)
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if (*lvalp > UINT_MAX)
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return -EINVAL;
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if (*lvalp > UINT_MAX)
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return -EINVAL;
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*valp = *lvalp;
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} else {
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unsigned int val = *valp;
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*negp = false;
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*lvalp = (unsigned long)val;
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}
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return 0;
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@ -2287,6 +2286,146 @@ static int do_proc_dointvec(struct ctl_table *table, int write,
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buffer, lenp, ppos, conv, data);
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}
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static int do_proc_douintvec_w(unsigned int *tbl_data,
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struct ctl_table *table,
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void __user *buffer,
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size_t *lenp, loff_t *ppos,
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int (*conv)(unsigned long *lvalp,
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unsigned int *valp,
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int write, void *data),
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void *data)
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{
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unsigned long lval;
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int err = 0;
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size_t left;
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bool neg;
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char *kbuf = NULL, *p;
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left = *lenp;
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if (proc_first_pos_non_zero_ignore(ppos, table))
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goto bail_early;
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if (left > PAGE_SIZE - 1)
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left = PAGE_SIZE - 1;
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p = kbuf = memdup_user_nul(buffer, left);
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if (IS_ERR(kbuf))
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return -EINVAL;
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left -= proc_skip_spaces(&p);
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if (!left) {
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err = -EINVAL;
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goto out_free;
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}
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err = proc_get_long(&p, &left, &lval, &neg,
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proc_wspace_sep,
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sizeof(proc_wspace_sep), NULL);
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if (err || neg) {
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err = -EINVAL;
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goto out_free;
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}
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if (conv(&lval, tbl_data, 1, data)) {
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err = -EINVAL;
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goto out_free;
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}
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if (!err && left)
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left -= proc_skip_spaces(&p);
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out_free:
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kfree(kbuf);
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if (err)
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return -EINVAL;
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return 0;
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/* This is in keeping with old __do_proc_dointvec() */
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bail_early:
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*ppos += *lenp;
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return err;
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}
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static int do_proc_douintvec_r(unsigned int *tbl_data, void __user *buffer,
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size_t *lenp, loff_t *ppos,
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int (*conv)(unsigned long *lvalp,
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unsigned int *valp,
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int write, void *data),
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void *data)
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{
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unsigned long lval;
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int err = 0;
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size_t left;
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left = *lenp;
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if (conv(&lval, tbl_data, 0, data)) {
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err = -EINVAL;
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goto out;
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}
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err = proc_put_long(&buffer, &left, lval, false);
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if (err || !left)
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goto out;
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err = proc_put_char(&buffer, &left, '\n');
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out:
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*lenp -= left;
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*ppos += *lenp;
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return err;
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}
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static int __do_proc_douintvec(void *tbl_data, struct ctl_table *table,
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int write, void __user *buffer,
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size_t *lenp, loff_t *ppos,
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int (*conv)(unsigned long *lvalp,
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unsigned int *valp,
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int write, void *data),
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void *data)
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{
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unsigned int *i, vleft;
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if (!tbl_data || !table->maxlen || !*lenp || (*ppos && !write)) {
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*lenp = 0;
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return 0;
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}
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i = (unsigned int *) tbl_data;
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vleft = table->maxlen / sizeof(*i);
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/*
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* Arrays are not supported, keep this simple. *Do not* add
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* support for them.
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*/
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if (vleft != 1) {
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*lenp = 0;
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return -EINVAL;
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}
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if (!conv)
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conv = do_proc_douintvec_conv;
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if (write)
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return do_proc_douintvec_w(i, table, buffer, lenp, ppos,
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conv, data);
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return do_proc_douintvec_r(i, buffer, lenp, ppos, conv, data);
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}
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static int do_proc_douintvec(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp, loff_t *ppos,
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int (*conv)(unsigned long *lvalp,
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unsigned int *valp,
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int write, void *data),
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void *data)
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{
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return __do_proc_douintvec(table->data, table, write,
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buffer, lenp, ppos, conv, data);
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}
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/**
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* proc_dointvec - read a vector of integers
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* @table: the sysctl table
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@ -2322,8 +2461,8 @@ int proc_dointvec(struct ctl_table *table, int write,
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int proc_douintvec(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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return do_proc_dointvec(table, write, buffer, lenp, ppos,
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do_proc_douintvec_conv, NULL);
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return do_proc_douintvec(table, write, buffer, lenp, ppos,
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do_proc_douintvec_conv, NULL);
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}
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/*
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