powerpc/kexec_file: Use inclusive range checks in add_usable_mem()

add_usable_mem() adds usable memory ranges for the kdump kernel.

The ranges are inclusive, but the partial overlap check uses exclusive comparisons. This skips ranges with base == loc_end or end == loc_base. Use inclusive comparisons instead.

Fixes 7c64e21a1c5a ("powerpc/kexec_file: Restrict memory usage of kdump kernel")

Signed-off-by Thorsten Blum <[email protected]>

---
  arch/powerpc/kexec/file_load_64.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

arch/powerpc/kexec/file_load_64.c +0 -0

index 8c72e12ea44e..f9e872693ca7 100644

arch/powerpc/kexec/file_load_64.c +0 -0

  			if (loc_base < base)
  				loc_base = base;
  			if (loc_end > end)

Quoted 17 lines · Thorsten Blum

add_usable_mem() adds usable memory ranges for the kdump kernel.

The ranges are inclusive, but the partial overlap check uses exclusive comparisons. This skips ranges with base == loc_end or end == loc_base. Use inclusive comparisons instead.

Fixes 7c64e21a1c5a ("powerpc/kexec_file: Restrict memory usage of kdump kernel")

Signed-off-by Thorsten Blum <[email protected]>

---
  arch/powerpc/kexec/file_load_64.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

arch/powerpc/kexec/file_load_64.c +0 -0

index 8c72e12ea44e..f9e872693ca7 100644

arch/powerpc/kexec/file_load_64.c static int add_usable_mem(struct umem_info *um_info, u64 base, u64 end) · line 116

Quoted 5 lines

arch/powerpc/kexec/file_load_64.c +1 -1

@@ -113,7 +113,7 @@ static int add_usable_mem(struct umem_info *um_info, u64 base, u64 end)
  		loc_end = um_info->ranges[i].end;
  		if (loc_base >= base && loc_end <= end)
  			add = true;
-		else if (base < loc_end && end > loc_base) {
+		else if (base <= loc_end && end >= loc_base) {

This is interesting. The updated condition basically handles exactly a one-byte overlap on either side of the usable memory ranges. In practice, it is very unlikely that we would have such usable memory and LMB ranges.

Thorsten, have you encountered any problem that led you to propose this fix?

Quoted 27 lines · Sourabh Jain

Quoted 17 lines · Thorsten Blum

add_usable_mem() adds usable memory ranges for the kdump kernel.

The ranges are inclusive, but the partial overlap check uses exclusive comparisons. This skips ranges with base == loc_end or end == loc_base. Use inclusive comparisons instead.

Fixes 7c64e21a1c5a ("powerpc/kexec_file: Restrict memory usage of kdump kernel")

Signed-off-by Thorsten Blum <[email protected]>

---
   arch/powerpc/kexec/file_load_64.c | 2 +-
   1 file changed, 1 insertion(+), 1 deletion(-)

arch/powerpc/kexec/file_load_64.c +0 -0

index 8c72e12ea44e..f9e872693ca7 100644

arch/powerpc/kexec/file_load_64.c static int add_usable_mem(struct umem_info *um_info, u64 base, u64 end) · line 116

Quoted 5 lines

arch/powerpc/kexec/file_load_64.c +1 -1

@@ -113,7 +113,7 @@ static int add_usable_mem(struct umem_info *um_info, u64 base, u64 end)
   		loc_end = um_info->ranges[i].end;
   		if (loc_base >= base && loc_end <= end)
   			add = true;
-		else if (base < loc_end && end > loc_base) {
+		else if (base <= loc_end && end >= loc_base) {

This is interesting. The updated condition basically handles exactly a one-byte overlap on either side of the usable memory ranges. In practice, it is very unlikely that we would have such usable memory and LMB ranges.

Quoted 1 line

Thorsten, have you encountered any problem that led you to propose this fix?

Found by inspection only and I agree that this is unlikely in practice, which is why I didn't cc stable. Same for the other patch [1].

Thanks for the review.

[1] https://lore.kernel.org/r/[email protected]/

add_usable_mem() adds usable memory ranges for the kdump kernel.

The ranges are inclusive, but the partial overlap check uses exclusive comparisons. This skips ranges with base == loc_end or end == loc_base. Use inclusive comparisons instead.

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