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Commit 440a6cc6 authored by Tobin C. Harding's avatar Tobin C. Harding Committed by Alistair Strachan
Browse files

BACKPORT: vsprintf: refactor %pK code out of pointer() 



Currently code to handle %pK is all within the switch statement in
pointer(). This is the wrong level of abstraction. Each of the other switch
clauses call a helper function, pK should do the same.

Refactor code out of pointer() to new function restricted_pointer().

Signed-off-by: default avatarTobin C. Harding <me@tobin.cc>
(cherry picked from commit 57e734423adda83f3b05505875343284efe3b39c)
Signed-off-by: default avatarSandeep Patil <sspatil@android.com>

Bug: 78533979
Test: Build and boot cuttlefish
Change-Id: Ib08350851ab0e99a3569c2c2e12aa421fb6bc622
parent b4d4c265

lib/vsprintf.c

+54 −43
Original line number Diff line number Diff line
@@ -1342,6 +1342,59 @@ char *uuid_string(char *buf, char *end, const u8 *addr, 
	return string(buf, end, uuid, spec);

}



int kptr_restrict __read_mostly;



static noinline_for_stack

char *restricted_pointer(char *buf, char *end, const void *ptr,

			 struct printf_spec spec)

{

	spec.base = 16;

	spec.flags |= SMALL;

	if (spec.field_width == -1) {

		spec.field_width = 2 * sizeof(ptr);

		spec.flags |= ZEROPAD;

	}



	switch (kptr_restrict) {

	case 0:

		/* Always print %pK values */

		break;

	case 1: {

		const struct cred *cred;



		/*

		 * kptr_restrict==1 cannot be used in IRQ context

		 * because its test for CAP_SYSLOG would be meaningless.

		 */

		if (in_irq() || in_serving_softirq() || in_nmi())

			return string(buf, end, "pK-error", spec);



		/*

		 * Only print the real pointer value if the current

		 * process has CAP_SYSLOG and is running with the

		 * same credentials it started with. This is because

		 * access to files is checked at open() time, but %pK

		 * checks permission at read() time. We don't want to

		 * leak pointer values if a binary opens a file using

		 * %pK and then elevates privileges before reading it.

		 */

		cred = current_cred();

		if (!has_capability_noaudit(current, CAP_SYSLOG) ||

		    !uid_eq(cred->euid, cred->uid) ||

		    !gid_eq(cred->egid, cred->gid))

			ptr = NULL;

		break;

	}

	case 2:

	default:

		/* Always print 0's for %pK */

		ptr = NULL;

		break;

	}



	return number(buf, end, (unsigned long)ptr, spec);

}



static noinline_for_stack

char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)

{
@@ -1467,8 +1520,6 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) 
	return format_flags(buf, end, flags, names);

}



int kptr_restrict __read_mostly;



/*

 * Show a '%p' thing.  A kernel extension is that the '%p' is followed

 * by an extra set of alphanumeric characters that are extended format
@@ -1655,47 +1706,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, 
			return buf;

		}

	case 'K':

		switch (kptr_restrict) {

		case 0:

			/* Always print %pK values */

			break;

		case 1: {

			const struct cred *cred;



			/*

			 * kptr_restrict==1 cannot be used in IRQ context

			 * because its test for CAP_SYSLOG would be meaningless.

			 */

			if (in_irq() || in_serving_softirq() || in_nmi()) {

				if (spec.field_width == -1)

					spec.field_width = default_width;

				return string(buf, end, "pK-error", spec);

			}



			/*

			 * Only print the real pointer value if the current

			 * process has CAP_SYSLOG and is running with the

			 * same credentials it started with. This is because

			 * access to files is checked at open() time, but %pK

			 * checks permission at read() time. We don't want to

			 * leak pointer values if a binary opens a file using

			 * %pK and then elevates privileges before reading it.

			 */

			cred = current_cred();

			if (!has_capability_noaudit(current, CAP_SYSLOG) ||

			    !uid_eq(cred->euid, cred->uid) ||

			    !gid_eq(cred->egid, cred->gid))

				ptr = NULL;

			break;

		}

		case 2:

		default:

			/* Always print 0's for %pK */

			ptr = NULL;

			break;

		}

		break;



		return restricted_pointer(buf, end, ptr, spec);

	case 'N':

		return netdev_bits(buf, end, ptr, fmt);

	case 'a':